tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF)
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".
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
- Added to Heist Feed
- Publisher date