nfnetlink_osf: validate individual option lengths in fingerprints

{
  "id": "79696fe1ec6d14a511f95b8d1f6e90809de09701337019317dc7683afc0641a1",
  "url": "https://osv.dev/vulnerability/CVE-2026-23397",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "nfnetlink_osf: validate individual option lengths in fingerprints",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: nfnetlink_osf: validate individual option lengths in fingerprints nfnl_osf_add_callback() validates opt_num bounds and string NUL-termination but does not check individual option length fields. A zero-length option causes nf_osf_match_one() to enter the option matching loop even when foptsize sums to zero, which matches packets with no TCP options where ctx->optp is NULL: Oops: general protection fault KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98) Call Trace: nf_osf_match (net/netfilter/nfnetlink_osf.c:227) xt_osf_match_packet (net/netfilter/xt_osf.c:32) ipt_do_table (net/ipv4/netfilter/ip_tables.c:293) nf_hook_slow (net/netfilter/core.c:623) ip_local_deliver (net/ipv4/ip_input.c:262) ip_rcv (net/ipv4/ip_input.c:573) Additionally, an MSS option (kind=2) with length < 4 causes out-of-bounds reads when nf_osf_match_one() unconditionally accesses optp[2] and optp[3] for MSS value extraction. While RFC 9293 section 3.2 specifies that the MSS option is always exactly 4 bytes (Kind=2, Length=4), the check uses \"< 4\" rather than \"!= 4\" because lengths greater than 4 do not cause memory safety issues -- the buffer is guaranteed to be at least foptsize bytes by the ctx->optsize == foptsize check. Reject fingerprints where any option has zero length, or where an MSS option has length less than 4, at add time rather than trusting thes",
    "evidence": "osv:CVE-2026-23397",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.253",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.203",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.167",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.130",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.78",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.20",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.10",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-23397",
      "aliases": [
        "CVE-2026-23397"
      ],
      "affected": [
        {
          "ranges": [
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
                  "fixed": "e9cf17b91e733fec725ebcc0b3098bc5ccd505e0"
                },
                {
                  "fixed": "3c11b5c2436a3a5b450612ab160e3a525b28cfb5"
                },
                {
                  "fixed": "aa0574182c46963c3cdb8cde46ec93aca21100d8"
                },
                {
                  "fixed": "224f4678812e1a7bc8341bcb666773a0aec5ea6f"
                },
                {
                  "fixed": "ec8bf0571b142f29dc0b68ae2ac3952f7a464b38"
                },
                {
                  "fixed": "3932620c04c2938c93c0890c225960d3d34ba355"
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                {
                  "fixed": "4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6"
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                {
                  "fixed": "dbdfaae9609629a9569362e3b8f33d0a20fd783c"
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              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23397.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "2.6.31"
                },
                {
                  "fixed": "5.10.253"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
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                {
                  "introduced": "5.11.0"
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                {
                  "fixed": "5.15.203"
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              ]
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            {
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                  "introduced": "5.16.0"
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                  "introduced": "6.2.0"
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            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.7.0"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.13.0"
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                {
                  "fixed": "6.18.20"
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                  "introduced": "6.19.0"
                },
                {
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              ]
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23397.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.382621353Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-019113.html",
        "https://cert-portal.siemens.com/productcert/html/ssa-082556.html",
        "https://cert-portal.siemens.com/productcert/html/ssa-457936.html",
        "https://cert-portal.siemens.com/productcert/html/ssa-784472.html",
        "https://git.kernel.org/stable/c/224f4678812e1a7bc8341bcb666773a0aec5ea6f",
        "https://git.kernel.org/stable/c/3932620c04c2938c93c0890c225960d3d34ba355",
        "https://git.kernel.org/stable/c/3c11b5c2436a3a5b450612ab160e3a525b28cfb5",
        "https://git.kernel.org/stable/c/4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6",
        "https://git.kernel.org/stable/c/aa0574182c46963c3cdb8cde46ec93aca21100d8",
        "https://git.kernel.org/stable/c/dbdfaae9609629a9569362e3b8f33d0a20fd783c",
        "https://git.kernel.org/stable/c/e9cf17b91e733fec725ebcc0b3098bc5ccd505e0",
        "https://git.kernel.org/stable/c/ec8bf0571b142f29dc0b68ae2ac3952f7a464b38",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23397.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-23397",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23397.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-23397",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 496968,
  "published_at": "2026-03-26T10:22:49.954+00:00"
}