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CVE-2025-21756 (GCVE-0-2025-21756)

Vulnerability from cvelistv5 – Published: 2025-02-27 02:18 – Updated: 2026-08-05 11:54
VLAI
Title
vsock: Keep the binding until socket destruction
Summary
In the Linux kernel, the following vulnerability has been resolved: vsock: Keep the binding until socket destruction Preserve sockets bindings; this includes both resulting from an explicit bind() and those implicitly bound through autobind during connect(). Prevents socket unbinding during a transport reassignment, which fixes a use-after-free: 1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2) 2. transport->release() calls vsock_remove_bound() without checking if sk was bound and moved to bound list (refcnt=1) 3. vsock_bind() assumes sk is in unbound list and before __vsock_insert_bound(vsock_bound_sockets()) calls __vsock_remove_bound() which does: list_del_init(&vsk->bound_table); // nop sock_put(&vsk->sk); // refcnt=0 BUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730 Read of size 4 at addr ffff88816b46a74c by task a.out/2057 dump_stack_lvl+0x68/0x90 print_report+0x174/0x4f6 kasan_report+0xb9/0x190 __vsock_bind+0x62e/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Allocated by task 2057: kasan_save_stack+0x1e/0x40 kasan_save_track+0x10/0x30 __kasan_slab_alloc+0x85/0x90 kmem_cache_alloc_noprof+0x131/0x450 sk_prot_alloc+0x5b/0x220 sk_alloc+0x2c/0x870 __vsock_create.constprop.0+0x2e/0xb60 vsock_create+0xe4/0x420 __sock_create+0x241/0x650 __sys_socket+0xf2/0x1a0 __x64_sys_socket+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Freed by task 2057: kasan_save_stack+0x1e/0x40 kasan_save_track+0x10/0x30 kasan_save_free_info+0x37/0x60 __kasan_slab_free+0x4b/0x70 kmem_cache_free+0x1a1/0x590 __sk_destruct+0x388/0x5a0 __vsock_bind+0x5e1/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e refcount_t: addition on 0; use-after-free. WARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150 RIP: 0010:refcount_warn_saturate+0xce/0x150 __vsock_bind+0x66d/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e refcount_t: underflow; use-after-free. WARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150 RIP: 0010:refcount_warn_saturate+0xee/0x150 vsock_remove_bound+0x187/0x1e0 __vsock_release+0x383/0x4a0 vsock_release+0x90/0x120 __sock_release+0xa3/0x250 sock_close+0x14/0x20 __fput+0x359/0xa80 task_work_run+0x107/0x1d0 do_exit+0x847/0x2560 do_group_exit+0xb8/0x250 __x64_sys_exit_group+0x3a/0x50 x64_sys_call+0xfec/0x14f0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: poc Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-08-14 21:01 UTC
CWE
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: c0cfa2d8a788fcf45df5bf4070ab2474c88d543a , < e7754d564579a5db9c5c9f74228df5d6dd6f1173 (git)
Affected: c0cfa2d8a788fcf45df5bf4070ab2474c88d543a , < e48fcb403c2d0e574c19683f09399ab4cf67809c (git)
Affected: c0cfa2d8a788fcf45df5bf4070ab2474c88d543a , < 42b33381e5e1f2b967dc4fb4221ddb9aaf10d197 (git)
Affected: c0cfa2d8a788fcf45df5bf4070ab2474c88d543a , < 3f43540166128951cc1be7ab1ce6b7f05c670d8b (git)
Affected: c0cfa2d8a788fcf45df5bf4070ab2474c88d543a , < 645ce25aa0e67895b11d89f27bb86c9d444c40f8 (git)
Affected: c0cfa2d8a788fcf45df5bf4070ab2474c88d543a , < b1afd40321f1c243cffbcf40ea7ca41aca87fa5e (git)
Affected: c0cfa2d8a788fcf45df5bf4070ab2474c88d543a , < fcdd2242c0231032fc84e1404315c245ae56322a (git)
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Linux Linux Affected: 5.5
Unaffected: 0 , < 5.5 (semver)
Unaffected: 5.10.235 , ≤ 5.10.* (semver)
Unaffected: 5.15.179 , ≤ 5.15.* (semver)
Unaffected: 6.1.131 , ≤ 6.1.* (semver)
Unaffected: 6.6.79 , ≤ 6.6.* (semver)
Unaffected: 6.12.16 , ≤ 6.12.* (semver)
Unaffected: 6.13.4 , ≤ 6.13.* (semver)
Unaffected: 6.14 , ≤ * (original_commit_for_fix)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem Affected: 0 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvsock: Keep the binding until socket destruction\n\nPreserve sockets bindings; this includes both resulting from an explicit\nbind() and those implicitly bound through autobind during connect().\n\nPrevents socket unbinding during a transport reassignment, which fixes a\nuse-after-free:\n\n    1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2)\n    2. transport-\u003erelease() calls vsock_remove_bound() without checking if\n       sk was bound and moved to bound list (refcnt=1)\n    3. vsock_bind() assumes sk is in unbound list and before\n       __vsock_insert_bound(vsock_bound_sockets()) calls\n       __vsock_remove_bound() which does:\n           list_del_init(\u0026vsk-\u003ebound_table); // nop\n           sock_put(\u0026vsk-\u003esk);               // refcnt=0\n\nBUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730\nRead of size 4 at addr ffff88816b46a74c by task a.out/2057\n dump_stack_lvl+0x68/0x90\n print_report+0x174/0x4f6\n kasan_report+0xb9/0x190\n __vsock_bind+0x62e/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nAllocated by task 2057:\n kasan_save_stack+0x1e/0x40\n kasan_save_track+0x10/0x30\n __kasan_slab_alloc+0x85/0x90\n kmem_cache_alloc_noprof+0x131/0x450\n sk_prot_alloc+0x5b/0x220\n sk_alloc+0x2c/0x870\n __vsock_create.constprop.0+0x2e/0xb60\n vsock_create+0xe4/0x420\n __sock_create+0x241/0x650\n __sys_socket+0xf2/0x1a0\n __x64_sys_socket+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nFreed by task 2057:\n kasan_save_stack+0x1e/0x40\n kasan_save_track+0x10/0x30\n kasan_save_free_info+0x37/0x60\n __kasan_slab_free+0x4b/0x70\n kmem_cache_free+0x1a1/0x590\n __sk_destruct+0x388/0x5a0\n __vsock_bind+0x5e1/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nrefcount_t: addition on 0; use-after-free.\nWARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150\nRIP: 0010:refcount_warn_saturate+0xce/0x150\n __vsock_bind+0x66d/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nrefcount_t: underflow; use-after-free.\nWARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150\nRIP: 0010:refcount_warn_saturate+0xee/0x150\n vsock_remove_bound+0x187/0x1e0\n __vsock_release+0x383/0x4a0\n vsock_release+0x90/0x120\n __sock_release+0xa3/0x250\n sock_close+0x14/0x20\n __fput+0x359/0xa80\n task_work_run+0x107/0x1d0\n do_exit+0x847/0x2560\n do_group_exit+0xb8/0x250\n __x64_sys_exit_group+0x3a/0x50\n x64_sys_call+0xfec/0x14f0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e"
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    "datePublished": "2025-02-27T02:18:11.547Z",
    "dateReserved": "2024-12-29T08:45:45.760Z",
    "dateUpdated": "2026-08-05T11:54:09.890Z",
    "state": "PUBLISHED"
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      "url": "https://msrc.microsoft.com/csaf/vex/2025/msrc_cve-2025-21756.json",
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvsock: Keep the binding until socket destruction\n\nPreserve sockets bindings; this includes both resulting from an explicit\nbind() and those implicitly bound through autobind during connect().\n\nPrevents socket unbinding during a transport reassignment, which fixes a\nuse-after-free:\n\n    1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2)\n    2. transport-\u003erelease() calls vsock_remove_bound() without checking if\n       sk was bound and moved to bound list (refcnt=1)\n    3. vsock_bind() assumes sk is in unbound list and before\n       __vsock_insert_bound(vsock_bound_sockets()) calls\n       __vsock_remove_bound() which does:\n           list_del_init(\u0026vsk-\u003ebound_table); // nop\n           sock_put(\u0026vsk-\u003esk);               // refcnt=0\n\nBUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730\nRead of size 4 at addr ffff88816b46a74c by task a.out/2057\n dump_stack_lvl+0x68/0x90\n print_report+0x174/0x4f6\n kasan_report+0xb9/0x190\n __vsock_bind+0x62e/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nAllocated by task 2057:\n kasan_save_stack+0x1e/0x40\n kasan_save_track+0x10/0x30\n __kasan_slab_alloc+0x85/0x90\n kmem_cache_alloc_noprof+0x131/0x450\n sk_prot_alloc+0x5b/0x220\n sk_alloc+0x2c/0x870\n __vsock_create.constprop.0+0x2e/0xb60\n vsock_create+0xe4/0x420\n __sock_create+0x241/0x650\n __sys_socket+0xf2/0x1a0\n __x64_sys_socket+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nFreed by task 2057:\n kasan_save_stack+0x1e/0x40\n kasan_save_track+0x10/0x30\n kasan_save_free_info+0x37/0x60\n __kasan_slab_free+0x4b/0x70\n kmem_cache_free+0x1a1/0x590\n __sk_destruct+0x388/0x5a0\n __vsock_bind+0x5e1/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nrefcount_t: addition on 0; use-after-free.\nWARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150\nRIP: 0010:refcount_warn_saturate+0xce/0x150\n __vsock_bind+0x66d/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nrefcount_t: underflow; use-after-free.\nWARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150\nRIP: 0010:refcount_warn_saturate+0xee/0x150\n vsock_remove_bound+0x187/0x1e0\n __vsock_release+0x383/0x4a0\n vsock_release+0x90/0x120\n __sock_release+0xa3/0x250\n sock_close+0x14/0x20\n __fput+0x359/0xa80\n task_work_run+0x107/0x1d0\n do_exit+0x847/0x2560\n do_group_exit+0xb8/0x250\n __x64_sys_exit_group+0x3a/0x50\n x64_sys_call+0xfec/0x14f0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e"
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: vsock: Mantener la vinculaci\u00f3n hasta la destrucci\u00f3n del socket Preservar las vinculaciones de los sockets; esto incluye tanto las resultantes de un bind() expl\u00edcito como las vinculadas impl\u00edcitamente a trav\u00e9s de autobind durante connect(). Evita la desvinculaci\u00f3n de sockets durante una reasignaci\u00f3n de transporte, lo que soluciona un use after free: 1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2) 2. transport-\u0026gt;release() calls vsock_remove_bound() without checking if sk was bound and moved to bound list (refcnt=1) 3. vsock_bind() assumes sk is in unbound list and before __vsock_insert_bound(vsock_bound_sockets()) calls __vsock_remove_bound() which does: list_del_init(\u0026amp;vsk-\u0026gt;bound_table); // nop sock_put(\u0026amp;vsk-\u0026gt;sk); // refcnt=0 BUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730 Read of size 4 at addr ffff88816b46a74c by task a.out/2057 dump_stack_lvl+0x68/0x90 print_report+0x174/0x4f6 kasan_report+0xb9/0x190 __vsock_bind+0x62e/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Allocated by task 2057: kasan_save_stack+0x1e/0x40 kasan_save_track+0x10/0x30 __kasan_slab_alloc+0x85/0x90 kmem_cache_alloc_noprof+0x131/0x450 sk_prot_alloc+0x5b/0x220 sk_alloc+0x2c/0x870 __vsock_create.constprop.0+0x2e/0xb60 vsock_create+0xe4/0x420 __sock_create+0x241/0x650 __sys_socket+0xf2/0x1a0 __x64_sys_socket+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Freed by task 2057: kasan_save_stack+0x1e/0x40 kasan_save_track+0x10/0x30 kasan_save_free_info+0x37/0x60 __kasan_slab_free+0x4b/0x70 kmem_cache_free+0x1a1/0x590 __sk_destruct+0x388/0x5a0 __vsock_bind+0x5e1/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e refcount_t: addition on 0; use-after-free. WARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150 RIP: 0010:refcount_warn_saturate+0xce/0x150 __vsock_bind+0x66d/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e refcount_t: underflow; use-after-free. WARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150 RIP: 0010:refcount_warn_saturate+0xee/0x150 vsock_remove_bound+0x187/0x1e0 __vsock_release+0x383/0x4a0 vsock_release+0x90/0x120 __sock_release+0xa3/0x250 sock_close+0x14/0x20 __fput+0x359/0xa80 task_work_run+0x107/0x1d0 do_exit+0x847/0x2560 do_group_exit+0xb8/0x250 __x64_sys_exit_group+0x3a/0x50 x64_sys_call+0xfec/0x14f0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e "
          }
        ],
        "id": "CVE-2025-21756",
        "lastModified": "2026-06-17T08:44:11.970",
        "metrics": {
          "cvssMetricV31": [
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                "attackVector": "LOCAL",
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                "baseScore": 7.8,
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                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
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                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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                    "automatable": "no"
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                  {
                    "technicalImpact": "total"
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                ],
                "role": "CISA Coordinator",
                "timestamp": "2025-08-14T21:01:56.187542Z",
                "version": "2.0.3"
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        "published": "2025-02-27T03:15:16.250",
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            "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
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    "redhat_vex": {
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      "current_release_date": "2026-06-29T20:34:42+00:00",
      "cve": "CVE-2025-21756",
      "id": "CVE-2025-21756",
      "initial_release_date": "2025-02-27T00:00:00+00:00",
      "product_status:fixed": "2308",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: vsock: Keep the binding until socket destruction",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21756.json",
      "version": "3"
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    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-08-30T02:05:27Z",
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      "initial_release_date": "2025-02-28T02:21:20Z",
      "product_status:known_affected": "353",
      "product_status:known_not_affected": "282",
      "product_status:recommended": "671",
      "source": "SUSE CSAF VEX",
      "status": "interim",
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      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-21756.json",
      "version": "66"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
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            "providerMetadata": {
              "dateUpdated": "2025-11-03T19:37:01.186Z",
              "orgId": "af854a3a-2127-422b-91ae-364da2661108",
              "shortName": "CVE"
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            "references": [
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                "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"
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              {
                "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
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            ],
            "title": "CVE Program Container"
          },
          {
            "affected": [
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                "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
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                "defaultStatus": "unknown",
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                "vendor": "Siemens",
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              },
              {
                "defaultStatus": "unknown",
                "product": "SIMATIC S7-1500 TM MFP - GNU/Linux subsystem",
                "vendor": "Siemens",
                "versions": [
                  {
                    "lessThan": "*",
                    "status": "affected",
                    "version": "0",
                    "versionType": "custom"
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                ]
              },
              {
                "defaultStatus": "unknown",
                "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
                "vendor": "Siemens",
                "versions": [
                  {
                    "lessThan": "*",
                    "status": "affected",
                    "version": "V3.1.5",
                    "versionType": "custom"
                  }
                ]
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-07-14T12:39:57.826Z",
              "orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
              "shortName": "siemens-SADP"
            },
            "references": [
              {
                "url": "https://cert-portal.siemens.com/productcert/html/ssa-265688.html"
              },
              {
                "url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
              }
            ],
            "x_adpType": "supplier"
          },
          {
            "metrics": [
              {
                "cvssV3_1": {
                  "attackComplexity": "LOW",
                  "attackVector": "LOCAL",
                  "availabilityImpact": "HIGH",
                  "baseScore": 7.8,
                  "baseSeverity": "HIGH",
                  "confidentialityImpact": "HIGH",
                  "integrityImpact": "HIGH",
                  "privilegesRequired": "LOW",
                  "scope": "UNCHANGED",
                  "userInteraction": "NONE",
                  "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                  "version": "3.1"
                }
              },
              {
                "other": {
                  "content": {
                    "id": "CVE-2025-21756",
                    "options": [
                      {
                        "Exploitation": "poc"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "total"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2025-08-14T21:01:56.187542Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "problemTypes": [
              {
                "descriptions": [
                  {
                    "cweId": "CWE-416",
                    "description": "CWE-416 Use After Free",
                    "lang": "en",
                    "type": "CWE"
                  }
                ]
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2025-02-27T18:14:20.000Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "net/vmw_vsock/af_vsock.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "lessThan": "e7754d564579a5db9c5c9f74228df5d6dd6f1173",
                  "status": "affected",
                  "version": "c0cfa2d8a788fcf45df5bf4070ab2474c88d543a",
                  "versionType": "git"
                },
                {
                  "lessThan": "e48fcb403c2d0e574c19683f09399ab4cf67809c",
                  "status": "affected",
                  "version": "c0cfa2d8a788fcf45df5bf4070ab2474c88d543a",
                  "versionType": "git"
                },
                {
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                  "status": "affected",
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                  "versionType": "git"
                },
                {
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                  "status": "affected",
                  "version": "c0cfa2d8a788fcf45df5bf4070ab2474c88d543a",
                  "versionType": "git"
                },
                {
                  "lessThan": "645ce25aa0e67895b11d89f27bb86c9d444c40f8",
                  "status": "affected",
                  "version": "c0cfa2d8a788fcf45df5bf4070ab2474c88d543a",
                  "versionType": "git"
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                {
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                  "status": "affected",
                  "version": "c0cfa2d8a788fcf45df5bf4070ab2474c88d543a",
                  "versionType": "git"
                },
                {
                  "lessThan": "fcdd2242c0231032fc84e1404315c245ae56322a",
                  "status": "affected",
                  "version": "c0cfa2d8a788fcf45df5bf4070ab2474c88d543a",
                  "versionType": "git"
                }
              ]
            },
            {
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              "product": "Linux",
              "programFiles": [
                "net/vmw_vsock/af_vsock.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "5.5"
                },
                {
                  "lessThan": "5.5",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.10.*",
                  "status": "unaffected",
                  "version": "5.10.235",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.15.*",
                  "status": "unaffected",
                  "version": "5.15.179",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.1.*",
                  "status": "unaffected",
                  "version": "6.1.131",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.79",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.16",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.13.*",
                  "status": "unaffected",
                  "version": "6.13.4",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "6.14",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                      "versionStartIncluding": "5.5",
                      "vulnerable": true
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                      "vulnerable": true
                    },
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                      "versionEndExcluding": "6.12.16",
                      "versionStartIncluding": "5.5",
                      "vulnerable": true
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                    {
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                  "operator": "OR"
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          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvsock: Keep the binding until socket destruction\n\nPreserve sockets bindings; this includes both resulting from an explicit\nbind() and those implicitly bound through autobind during connect().\n\nPrevents socket unbinding during a transport reassignment, which fixes a\nuse-after-free:\n\n    1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2)\n    2. transport-\u003erelease() calls vsock_remove_bound() without checking if\n       sk was bound and moved to bound list (refcnt=1)\n    3. vsock_bind() assumes sk is in unbound list and before\n       __vsock_insert_bound(vsock_bound_sockets()) calls\n       __vsock_remove_bound() which does:\n           list_del_init(\u0026vsk-\u003ebound_table); // nop\n           sock_put(\u0026vsk-\u003esk);               // refcnt=0\n\nBUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730\nRead of size 4 at addr ffff88816b46a74c by task a.out/2057\n dump_stack_lvl+0x68/0x90\n print_report+0x174/0x4f6\n kasan_report+0xb9/0x190\n __vsock_bind+0x62e/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nAllocated by task 2057:\n kasan_save_stack+0x1e/0x40\n kasan_save_track+0x10/0x30\n __kasan_slab_alloc+0x85/0x90\n kmem_cache_alloc_noprof+0x131/0x450\n sk_prot_alloc+0x5b/0x220\n sk_alloc+0x2c/0x870\n __vsock_create.constprop.0+0x2e/0xb60\n vsock_create+0xe4/0x420\n __sock_create+0x241/0x650\n __sys_socket+0xf2/0x1a0\n __x64_sys_socket+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nFreed by task 2057:\n kasan_save_stack+0x1e/0x40\n kasan_save_track+0x10/0x30\n kasan_save_free_info+0x37/0x60\n __kasan_slab_free+0x4b/0x70\n kmem_cache_free+0x1a1/0x590\n __sk_destruct+0x388/0x5a0\n __vsock_bind+0x5e1/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nrefcount_t: addition on 0; use-after-free.\nWARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150\nRIP: 0010:refcount_warn_saturate+0xce/0x150\n __vsock_bind+0x66d/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nrefcount_t: underflow; use-after-free.\nWARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150\nRIP: 0010:refcount_warn_saturate+0xee/0x150\n vsock_remove_bound+0x187/0x1e0\n __vsock_release+0x383/0x4a0\n vsock_release+0x90/0x120\n __sock_release+0xa3/0x250\n sock_close+0x14/0x20\n __fput+0x359/0xa80\n task_work_run+0x107/0x1d0\n do_exit+0x847/0x2560\n do_group_exit+0xb8/0x250\n __x64_sys_exit_group+0x3a/0x50\n x64_sys_call+0xfec/0x14f0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e"
            }
          ],
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                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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                {
                  "lang": "en",
                  "value": "Deterministic UAF in vsock socket binding during transport reassignment. connect() unbinds the socket dropping refcount, then bind() triggers use-after-free exploitable for privilege escalation."
                }
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            }
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            "dateUpdated": "2026-08-05T11:54:09.890Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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              "url": "https://git.kernel.org/stable/c/e7754d564579a5db9c5c9f74228df5d6dd6f1173"
            },
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            },
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              "url": "https://git.kernel.org/stable/c/b1afd40321f1c243cffbcf40ea7ca41aca87fa5e"
            },
            {
              "url": "https://git.kernel.org/stable/c/fcdd2242c0231032fc84e1404315c245ae56322a"
            }
          ],
          "title": "vsock: Keep the binding until socket destruction",
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      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2025-21756",
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        "dateReserved": "2024-12-29T08:45:45.760Z",
        "dateUpdated": "2026-08-05T11:54:09.890Z",
        "state": "PUBLISHED"
      },
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    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.