CVE-2026-98241 (GCVE-0-2026-98241)
Vulnerability from cvelistv5
Published
2026-10-06 08:45
Modified
2026-10-19 09:16
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: xfrm: use full sockets in local error paths xfrm6_local_rxpmtu() and xfrm6_local_error() dereference skb->sk as if it always pointed at a full IPv6 socket. That is not guaranteed. TCP SYN-ACK skbs can be owned by a TCP_NEW_SYN_RECV request_sock while the output path itself is driven by the full listener. If rerouting selects an IPv6 XFRM tunnel route with a lower MTU, the local PMTU/error handling path can reach these callbacks with that mini-socket still attached to the skb. The callbacks then miscast the request socket as a full inet/IPv6 socket and can read beyond the request_sock allocation when they access inet_sock or ipv6_pinfo state. Resolve the owner with skb_to_full_sk() in both callbacks and bail out when no full socket is attached. This matches the surrounding XFRM IPv6 PMTU/error logic, which already reasons about full sockets with skb_to_full_sk().
References
Impacted products
Vendor Product Version
Linux Linux Version: dd767856a36e00b631d65ebc4bb81b19915532d6
Version: dd767856a36e00b631d65ebc4bb81b19915532d6
Version: dd767856a36e00b631d65ebc4bb81b19915532d6
Version: dd767856a36e00b631d65ebc4bb81b19915532d6
Version: dd767856a36e00b631d65ebc4bb81b19915532d6
Version: dd767856a36e00b631d65ebc4bb81b19915532d6
Version: dd767856a36e00b631d65ebc4bb81b19915532d6
Version: dd767856a36e00b631d65ebc4bb81b19915532d6
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/xfrm6_output.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
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              "status": "affected",
              "version": "dd767856a36e00b631d65ebc4bb81b19915532d6",
              "versionType": "git"
            },
            {
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              "status": "affected",
              "version": "dd767856a36e00b631d65ebc4bb81b19915532d6",
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            {
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              "status": "affected",
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              "versionType": "git"
            },
            {
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              "version": "dd767856a36e00b631d65ebc4bb81b19915532d6",
              "versionType": "git"
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            },
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              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/xfrm6_output.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "3.2"
            },
            {
              "lessThan": "3.2",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.271",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.222",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.189",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.158",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.112",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.54",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.271",
                  "versionStartIncluding": "3.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.222",
                  "versionStartIncluding": "3.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.189",
                  "versionStartIncluding": "3.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.158",
                  "versionStartIncluding": "3.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.112",
                  "versionStartIncluding": "3.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.54",
                  "versionStartIncluding": "3.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.8",
                  "versionStartIncluding": "3.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "3.2",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: xfrm: use full sockets in local error paths\n\nxfrm6_local_rxpmtu() and xfrm6_local_error() dereference skb-\u003esk as if it\nalways pointed at a full IPv6 socket.\n\nThat is not guaranteed. TCP SYN-ACK skbs can be owned by a\nTCP_NEW_SYN_RECV request_sock while the output path itself is driven by the\nfull listener. If rerouting selects an IPv6 XFRM tunnel route with a lower\nMTU, the local PMTU/error handling path can reach these callbacks with that\nmini-socket still attached to the skb.\n\nThe callbacks then miscast the request socket as a full inet/IPv6 socket and\ncan read beyond the request_sock allocation when they access inet_sock or\nipv6_pinfo state.\n\nResolve the owner with skb_to_full_sk() in both callbacks and bail out when\nno full socket is attached. This matches the surrounding XFRM IPv6 PMTU/error\nlogic, which already reasons about full sockets with skb_to_full_sk()."
        }
      ],
      "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 fixed xfrm6_local_error() is reached via __xfrm6_output() -\u003e xfrm_local_error() only if a rerouted SYN-ACK exceeds an xfrm tunnel MTU below ~100 bytes; that needs local xfrm/route/netfilter setup. A remote SYN carries no malformed data and can\u0027t create this state (IPv4 PMTU floor is 552, xfrm6_tunnel_check_size clamps to 1280).\nAC:L - The attacker builds every precondition: an IPv6-in-IPv4 tunnel-mode xfrm SA/policy, a tiny outer MTU, a LOCAL_OUT reroute, and a TCP listener they connect to. Each SYN deterministically sends a SYN-ACK owned by a TCP_NEW_SYN_RECV request_sock down the !ignore_df \u0026\u0026 toobig branch.\nPR:L - The needed XFRM_MSG_NEWSA/NEWPOLICY, nftables rules and link MTU changes only need CAP_NET_ADMIN in the netns, which an unprivileged user gets via unshare -Urn; the listener and connect() are ordinary syscalls.\nUI:N - The attacker sets up the namespace and drives the handshake that emits the SYN-ACK themselves; no other user has to do anything.\nS:U - The out-of-bounds access corrupts kernel heap memory in the same kernel that enforces the attacker\u0027s namespace; no hypervisor or IOMMU boundary is crossed.\nC:H - xfrm6_local_error() passes the request_sock to ipv6_local_error() as a full IPv6 socket; inet6_test_bit(RECVERR6) reads inet_flags past the end of the tcp6_request_sock allocation, into the next slab object, and the rest of the path keeps reading socket fields out of bounds.\nI:H - If the out-of-bounds RECVERR6 bit is set, sock_queue_err_skb() does atomic_add on an OOB sk_rmem_alloc, links an skb into an OOB sk_error_queue list and calls the OOB sk_error_report pointer: heap writes plus control-flow hijack if the attacker grooms the adjacent object.\nA:H - Treating neighbouring slab memory as sk_error_queue and sk_error_report gives list corruption or a wild indirect call, crashing the kernel; the attacker can repeat it with each SYN."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:16:12.796Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/b1a88633c36d2cbc3831382f3846754d344276fd"
        },
        {
          "url": "https://git.kernel.org/stable/c/904a0e827d0d7189271a3a2eb648293809f25efc"
        },
        {
          "url": "https://git.kernel.org/stable/c/675919e08ce266b8cac11fd9af29170e762a480f"
        },
        {
          "url": "https://git.kernel.org/stable/c/60459c670329d586a58db5d8f811fa5accfe4862"
        },
        {
          "url": "https://git.kernel.org/stable/c/ca3d68c3213475b53db6647e159dc73bd1af5ab1"
        },
        {
          "url": "https://git.kernel.org/stable/c/4c030a0400ebfd2318361c923a88103b2c67c49f"
        },
        {
          "url": "https://git.kernel.org/stable/c/c21f3f7fbfeda7c5794f606cb0ffcc2d9001eef8"
        },
        {
          "url": "https://git.kernel.org/stable/c/6973a21ee73c5567f883813c8ef414774b45892f"
        }
      ],
      "title": "ipv6: xfrm: use full sockets in local error paths",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98241",
    "datePublished": "2026-10-06T08:45:11.954Z",
    "dateReserved": "2026-09-25T10:25:14.329Z",
    "dateUpdated": "2026-10-19T09:16:12.796Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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