CVE-2026-45837 (GCVE-0-2026-45837)

Vulnerability from cvelistv5 – Published: 2026-05-27 09:24 – Updated: 2026-05-27 09:24
VLAI
Title
bpf: Fix use-after-free in arena_vm_close on fork
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix use-after-free in arena_vm_close on fork arena_vm_open() only bumps vml->mmap_count but never registers the child VMA in arena->vma_list. The vml->vma always points at the parent VMA, so after parent munmap the pointer dangles. If the child then calls bpf_arena_free_pages(), zap_pages() reads the stale vml->vma triggering use-after-free. Fix this by preventing the arena VMA from being inherited across fork with VM_DONTCOPY, and preventing VMA splits via the may_split callback. Also reject mremap with a .mremap callback returning -EINVAL. A same-size mremap(MREMAP_FIXED) on the full arena VMA reaches copy_vma() through the following path: check_prep_vma() - returns 0 early: new_len == old_len skips VM_DONTEXPAND check prep_move_vma() - vm_start == old_addr and vm_end == old_addr + old_len so may_split is never called move_vma() copy_vma_and_data() copy_vma() vm_area_dup() - copies vm_private_data (vml pointer) vm_ops->open() - bumps vml->mmap_count vm_ops->mremap() - returns -EINVAL, rollback unmaps new VMA The refcount ensures the rollback's arena_vm_close does not free the vml shared with the original VMA.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 317460317a02a1af512697e6e964298dedd8a163 , < 723b9fa930cc277c15ce6b9ec9feec828cfac9d7 (git)
Affected: 317460317a02a1af512697e6e964298dedd8a163 , < d18099f19e53250f8ad2801498b88cec29d9107a (git)
Affected: 317460317a02a1af512697e6e964298dedd8a163 , < 201128fcc7b213d27ab77bc4e89488b41796480f (git)
Affected: 317460317a02a1af512697e6e964298dedd8a163 , < 4fddde2a732de60bb97e3307d4eb69ac5f1d2b74 (git)
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Linux Linux Affected: 6.9
Unaffected: 0 , < 6.9 (semver)
Unaffected: 6.12.88 , ≤ 6.12.* (semver)
Unaffected: 6.18.30 , ≤ 6.18.* (semver)
Unaffected: 7.0.7 , ≤ 7.0.* (semver)
Unaffected: 7.1-rc1 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/arena.c"
          ],
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          "vendor": "Linux",
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          "vendor": "Linux",
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              "version": "0",
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              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.30",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "7.0.7",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.1-rc1",
              "versionType": "original_commit_for_fix"
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        }
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                  "versionStartIncluding": "6.9",
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                  "versionEndExcluding": "6.18.30",
                  "versionStartIncluding": "6.9",
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                },
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                  "versionEndExcluding": "7.0.7",
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                }
              ],
              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix use-after-free in arena_vm_close on fork\n\narena_vm_open() only bumps vml-\u003emmap_count but never registers the\nchild VMA in arena-\u003evma_list. The vml-\u003evma always points at the\nparent VMA, so after parent munmap the pointer dangles. If the child\nthen calls bpf_arena_free_pages(), zap_pages() reads the stale\nvml-\u003evma triggering use-after-free.\n\nFix this by preventing the arena VMA from being inherited across\nfork with VM_DONTCOPY, and preventing VMA splits via the may_split\ncallback.\n\nAlso reject mremap with a .mremap callback returning -EINVAL. A\nsame-size mremap(MREMAP_FIXED) on the full arena VMA reaches\ncopy_vma() through the following path:\n\n  check_prep_vma()       - returns 0 early: new_len == old_len\n                           skips VM_DONTEXPAND check\n  prep_move_vma()        - vm_start == old_addr and\n                           vm_end == old_addr + old_len\n                           so may_split is never called\n  move_vma()\n    copy_vma_and_data()\n      copy_vma()\n        vm_area_dup()    - copies vm_private_data (vml pointer)\n        vm_ops-\u003eopen()   - bumps vml-\u003emmap_count\n      vm_ops-\u003emremap()   - returns -EINVAL, rollback unmaps new VMA\n\nThe refcount ensures the rollback\u0027s arena_vm_close does not free\nthe vml shared with the original VMA."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-27T09:24:32.833Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/723b9fa930cc277c15ce6b9ec9feec828cfac9d7"
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          "url": "https://git.kernel.org/stable/c/d18099f19e53250f8ad2801498b88cec29d9107a"
        },
        {
          "url": "https://git.kernel.org/stable/c/201128fcc7b213d27ab77bc4e89488b41796480f"
        },
        {
          "url": "https://git.kernel.org/stable/c/4fddde2a732de60bb97e3307d4eb69ac5f1d2b74"
        }
      ],
      "title": "bpf: Fix use-after-free in arena_vm_close on fork",
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-45837",
    "datePublished": "2026-05-27T09:24:32.833Z",
    "dateReserved": "2026-05-13T15:03:33.077Z",
    "dateUpdated": "2026-05-27T09:24:32.833Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-45837",
      "date": "2026-05-28",
      "epss": "0.00018",
      "percentile": "0.04906"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-45837\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-05-27T11:16:23.020\",\"lastModified\":\"2026-05-27T14:48:03.013\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nbpf: Fix use-after-free in arena_vm_close on fork\\n\\narena_vm_open() only bumps vml-\u003emmap_count but never registers the\\nchild VMA in arena-\u003evma_list. The vml-\u003evma always points at the\\nparent VMA, so after parent munmap the pointer dangles. If the child\\nthen calls bpf_arena_free_pages(), zap_pages() reads the stale\\nvml-\u003evma triggering use-after-free.\\n\\nFix this by preventing the arena VMA from being inherited across\\nfork with VM_DONTCOPY, and preventing VMA splits via the may_split\\ncallback.\\n\\nAlso reject mremap with a .mremap callback returning -EINVAL. A\\nsame-size mremap(MREMAP_FIXED) on the full arena VMA reaches\\ncopy_vma() through the following path:\\n\\n  check_prep_vma()       - returns 0 early: new_len == old_len\\n                           skips VM_DONTEXPAND check\\n  prep_move_vma()        - vm_start == old_addr and\\n                           vm_end == old_addr + old_len\\n                           so may_split is never called\\n  move_vma()\\n    copy_vma_and_data()\\n      copy_vma()\\n        vm_area_dup()    - copies vm_private_data (vml pointer)\\n        vm_ops-\u003eopen()   - bumps vml-\u003emmap_count\\n      vm_ops-\u003emremap()   - returns -EINVAL, rollback unmaps new VMA\\n\\nThe refcount ensures the rollback\u0027s arena_vm_close does not free\\nthe vml shared with the original VMA.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/201128fcc7b213d27ab77bc4e89488b41796480f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4fddde2a732de60bb97e3307d4eb69ac5f1d2b74\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/723b9fa930cc277c15ce6b9ec9feec828cfac9d7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d18099f19e53250f8ad2801498b88cec29d9107a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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