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tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF)

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF) When MTU is large, ip6_default_advmss() can return IPV6_MAXPLEN (65535). This is interpreted by TCP as mss_clamp, allowing the MSS to reach 65535. However, 0xFFFF is also used as a magic value GSO_BY_FRAGS in the kernel. If a TCP packet with gso_size=0xFFFF is passed to skb_segment(), it will be mistakenly treated as GSO_BY_FRAGS, leading to a NULL pointer dereference because local TCP packets do not use frag_list. Fix this by returning min(IPV6_MAXPLEN, GSO_BY_FRAGS - 1) (65534) from ip6_default_advmss() when MTU is large. Also update the stale comment in ip6_default_advmss() which suggested that IPV6_MAXPLEN is returned to mean "any MSS".

Announced Source revision 1
Original source ↗

CVE-2026-72502

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-72502

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba",
        "lessThan": "560b33b434e922ef97f9ff23aa2e909ef7aacd5c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba",
        "lessThan": "21f69ac1879bb970588d5e7c12a96e6542f7c1a7",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba",
        "lessThan": "c0db3dc2ac323b6c4b76adede3b355a9daa6dea8",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba",
        "lessThan": "572fff10819dfc359298d1f774839e76a4d96f93",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba",
        "lessThan": "8e6214a530c03e341dc1b0a846c8f2b716b3551a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba",
        "lessThan": "d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba",
        "lessThan": "a210791f33345aa87187f7d7a9f3b9b7f4a28e6d",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba",
        "lessThan": "2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/ipv6/route.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "4.8"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "4.8",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.261",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.212",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.178",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.145",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.97",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.40",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.1.5",
        "versionType": "semver",
        "lessThanOrEqual": "7.1.*"
      },
      {
        "status": "unaffected",
        "version": "7.2",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/ipv6/route.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-72502

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#33068 · Revision 1
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Publisher date
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