CVE-2026-93105 (GCVE-0-2026-93105)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:11 – Updated: 2026-09-18 17:55
VLAI
Title
esp: do not unref managed frag pages in esp_ssg_unref()
Summary
In the Linux kernel, the following vulnerability has been resolved: esp: do not unref managed frag pages in esp_ssg_unref() esp_ssg_unref() releases the page references held on the source scatterlist after the AEAD operation completes. It calls skb_page_unref() on every frag page for an out-of-place transform (req->src != req->dst), and in the error path of esp_output_tail() (already_unref == true) on the request's own scatterlist. This is wrong when the skb carries managed frags (SKBFL_MANAGED_FRAG_REFS). Managed frags are owned by a zerocopy ubuf and the skb does not hold a per-frag page reference; io_uring SEND_ZC with a registered buffer attaches the bvec pages this way via io_sg_from_iter(). The rest of the stack honours this invariant: skb_release_data() skips the per-frag unref when SKBFL_MANAGED_FRAG_REFS is set, and skb_zcopy_managed() is the guard used at the other unref sites. esp_ssg_unref() is missing that guard, so for a managed-frag skb it drops a page reference the skb never acquired. This can underflow the page reference count and free a page that is still in use. Guard the function with skb_zcopy_managed() so both unref paths are skipped for managed-frag skbs, matching skb_release_data().
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: cac2661c53f35cbe651bef9b07026a5a05ab8ce0 , < 26b6b14c7a0368e317a1e9fb5144ebe6f8d495cf (git)
Affected: cac2661c53f35cbe651bef9b07026a5a05ab8ce0 , < 21697720ff43b8dfa25b8e8d9ca7f56f4597fc80 (git)
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Linux Linux Affected: 4.11
Unaffected: 0 , < 4.11 (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/esp4.c",
            "net/ipv6/esp6.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "versionType": "git"
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              "status": "affected",
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              "versionType": "git"
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          "product": "Linux",
          "programFiles": [
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
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          "nodes": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "4.11",
                  "vulnerable": true
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "4.11",
                  "vulnerable": true
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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\nesp: do not unref managed frag pages in esp_ssg_unref()\n\nesp_ssg_unref() releases the page references held on the source\nscatterlist after the AEAD operation completes.  It calls\nskb_page_unref() on every frag page for an out-of-place transform\n(req-\u003esrc != req-\u003edst), and in the error path of esp_output_tail()\n(already_unref == true) on the request\u0027s own scatterlist.\n\nThis is wrong when the skb carries managed frags\n(SKBFL_MANAGED_FRAG_REFS).  Managed frags are owned by a zerocopy ubuf\nand the skb does not hold a per-frag page reference; io_uring SEND_ZC\nwith a registered buffer attaches the bvec pages this way via\nio_sg_from_iter().  The rest of the stack honours this invariant:\nskb_release_data() skips the per-frag unref when SKBFL_MANAGED_FRAG_REFS\nis set, and skb_zcopy_managed() is the guard used at the other unref\nsites.\n\nesp_ssg_unref() is missing that guard, so for a managed-frag skb it\ndrops a page reference the skb never acquired.  This can underflow the\npage reference count and free a page that is still in use.\n\nGuard the function with skb_zcopy_managed() so both unref paths are\nskipped for managed-frag skbs, matching skb_release_data()."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The extra unref is reached from IORING_OP_SEND_ZC/SENDMSG_ZC with IORING_RECVSEND_FIXED_BUF: io_sendmsg_zc() -\u003e sock_sendmsg() -\u003e tcp_sendmsg_locked() -\u003e xfrm_output() -\u003e esp_output_tail() -\u003e esp_ssg_unref(). io_sg_from_iter() is the only site that sets SKBFL_MANAGED_FRAG_REFS; esp_input() never calls esp_ssg_unref(), so a remote ESP packet cannot supply the buggy skb.\nAC:L - tcp_stream_alloc_skb() allocates MAX_TCP_HEADER then skb_reserve()s all of it, so a SEND_ZC TCP skb has ~0 tailroom. esp_output_head() therefore takes inplace=false (tailen \u003e tailroom, nr_frags \u003c MAX_SKB_FRAGS, data_len+tailen \u003c= PAGE_SIZE), after which esp_output_tail() replaces the frags and esp_ssg_unref() always drops the managed pages. The attacker chooses the send size.\nPR:L - io_uring_setup() allows IORING_OP_SEND_ZC when sysctl_io_uring_disabled==0 (default); no capability is checked on that send path. An ESP SA is also required: the attacker can add one in a user+net namespace because xfrm_user_rcv_msg() only tests netlink_net_capable(CAP_NET_ADMIN) against the netns user_ns, or can send through an already-installed IPsec policy.\nUI:N - The attacker registers the buffer with IORING_REGISTER_BUFFERS, submits SEND_ZC, and if needed installs the XFRM state/policy; no other user must open a file, mount a volume, or otherwise act.\nS:U - esp_ssg_unref()\u0027s extra put_page() corrupts host kernel page refcounts. That is a conventional local privilege escalation inside the same kernel, not a KVM/Xen guest-to-host or IOMMU-scope change.\nC:H - After the out-of-place transform, esp_ssg_unref() calls skb_page_unref() on every source sg page past skb-\u003edata. Those pages were attached by io_sg_from_iter() without a per-frag get_page(), so the extra put underflows the refcount of still-mapped IORING_REGISTER_BUFFERS pages and frees memory the attacker can read.\nI:H - The same extra skb_page_unref() frees registered-buffer pages that remain in the io_uring bvec and the attacker\u0027s userspace mapping, so the page can be reallocated and overwritten, giving an arbitrary write and control-flow hijack.\nA:H - The extra put_page() on managed frag pages underflows the page refcount and frees a page still in use, which oopses with bad page state even when the use-after-free is not turned into a full memory-corruption exploit."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-18T17:55:56.276Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/26b6b14c7a0368e317a1e9fb5144ebe6f8d495cf"
        },
        {
          "url": "https://git.kernel.org/stable/c/21697720ff43b8dfa25b8e8d9ca7f56f4597fc80"
        }
      ],
      "title": "esp: do not unref managed frag pages in esp_ssg_unref()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-93105",
    "datePublished": "2026-09-17T16:11:16.442Z",
    "dateReserved": "2026-09-17T16:02:15.085Z",
    "dateUpdated": "2026-09-18T17:55:56.276Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "date": "2026-09-29",
      "epss": "0.00165",
      "percentile": "0.05078"
    },
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      "current_release_date": "2026-09-23T02:17:05.000Z",
      "cve": "CVE-2026-93105",
      "id": "msrc_CVE-2026-93105",
      "initial_release_date": "2026-09-19T01:16:23.000Z",
      "product_status:known_affected": "2",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "esp: do not unref managed frag pages in esp_ssg_unref()",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-93105.json",
      "version": "2"
    },
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      "cve": {
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                "product": "Linux",
                "programFiles": [
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                  "net/ipv6/esp6.c"
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                "vendor": "Linux",
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                    "version": "0",
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                    "version": "7.2.6",
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        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nesp: do not unref managed frag pages in esp_ssg_unref()\n\nesp_ssg_unref() releases the page references held on the source\nscatterlist after the AEAD operation completes.  It calls\nskb_page_unref() on every frag page for an out-of-place transform\n(req-\u003esrc != req-\u003edst), and in the error path of esp_output_tail()\n(already_unref == true) on the request\u0027s own scatterlist.\n\nThis is wrong when the skb carries managed frags\n(SKBFL_MANAGED_FRAG_REFS).  Managed frags are owned by a zerocopy ubuf\nand the skb does not hold a per-frag page reference; io_uring SEND_ZC\nwith a registered buffer attaches the bvec pages this way via\nio_sg_from_iter().  The rest of the stack honours this invariant:\nskb_release_data() skips the per-frag unref when SKBFL_MANAGED_FRAG_REFS\nis set, and skb_zcopy_managed() is the guard used at the other unref\nsites.\n\nesp_ssg_unref() is missing that guard, so for a managed-frag skb it\ndrops a page reference the skb never acquired.  This can underflow the\npage reference count and free a page that is still in use.\n\nGuard the function with skb_zcopy_managed() so both unref paths are\nskipped for managed-frag skbs, matching skb_release_data()."
          }
        ],
        "id": "CVE-2026-93105",
        "lastModified": "2026-09-18T18:18:20.667",
        "metrics": {
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              "cvssData": {
                "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"
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              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-09-17T17:18:04.847",
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/26b6b14c7a0368e317a1e9fb5144ebe6f8d495cf"
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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    "suse_vex": {
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      "current_release_date": "2026-09-22T16:24:30Z",
      "cve": "CVE-2026-93105",
      "id": "CVE-2026-93105",
      "initial_release_date": "2026-09-18T00:11:59Z",
      "product_status:known_affected": "341",
      "product_status:known_not_affected": "6",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-93105",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-93105.json",
      "version": "4"
    }
  }
}



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