GHSA-3RCM-5VQM-53W6

Vulnerability from github – Published: 2026-03-26 12:30 – Updated: 2026-03-26 12:30
VLAI?
Details

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 these values in the packet matching hot path.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-23397"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-03-26T11:16:19Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfnetlink_osf: validate individual option lengths in fingerprints\n\nnfnl_osf_add_callback() validates opt_num bounds and string\nNUL-termination but does not check individual option length fields.\nA zero-length option causes nf_osf_match_one() to enter the option\nmatching loop even when foptsize sums to zero, which matches packets\nwith no TCP options where ctx-\u003eoptp is NULL:\n\n Oops: general protection fault\n KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]\n RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98)\n Call Trace:\n  nf_osf_match (net/netfilter/nfnetlink_osf.c:227)\n  xt_osf_match_packet (net/netfilter/xt_osf.c:32)\n  ipt_do_table (net/ipv4/netfilter/ip_tables.c:293)\n  nf_hook_slow (net/netfilter/core.c:623)\n  ip_local_deliver (net/ipv4/ip_input.c:262)\n  ip_rcv (net/ipv4/ip_input.c:573)\n\nAdditionally, an MSS option (kind=2) with length \u003c 4 causes\nout-of-bounds reads when nf_osf_match_one() unconditionally accesses\noptp[2] and optp[3] for MSS value extraction.  While RFC 9293\nsection 3.2 specifies that the MSS option is always exactly 4\nbytes (Kind=2, Length=4), the check uses \"\u003c 4\" rather than\n\"!= 4\" because lengths greater than 4 do not cause memory\nsafety issues -- the buffer is guaranteed to be at least\nfoptsize bytes by the ctx-\u003eoptsize == foptsize check.\n\nReject fingerprints where any option has zero length, or where an MSS\noption has length less than 4, at add time rather than trusting these\nvalues in the packet matching hot path.",
  "id": "GHSA-3rcm-5vqm-53w6",
  "modified": "2026-03-26T12:30:29Z",
  "published": "2026-03-26T12:30:29Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23397"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/224f4678812e1a7bc8341bcb666773a0aec5ea6f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3932620c04c2938c93c0890c225960d3d34ba355"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/aa0574182c46963c3cdb8cde46ec93aca21100d8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dbdfaae9609629a9569362e3b8f33d0a20fd783c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ec8bf0571b142f29dc0b68ae2ac3952f7a464b38"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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