Vulnerability details
CVE-2026-72502
tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF)
Official description
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".
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 7.5High | 3.1 | CVEProject cvelistV5 (CNA) (Linux) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| Linux | Linux | 4.8 | CVEProject cvelistV5 (CNA) |
| Linux | Linux | 3953c46c3ac7eef31a9935427371c6f54a22f1ba ≤ v < 21f69ac1879bb970588d5e7c12a96e6542f7c1a7 | CVEProject cvelistV5 (CNA) |
| Linux | Linux | 3953c46c3ac7eef31a9935427371c6f54a22f1ba ≤ v < c0db3dc2ac323b6c4b76adede3b355a9daa6dea8 | CVEProject cvelistV5 (CNA) |
| Linux | Linux | 3953c46c3ac7eef31a9935427371c6f54a22f1ba ≤ v < 572fff10819dfc359298d1f774839e76a4d96f93 | CVEProject cvelistV5 (CNA) |
| Linux | Linux | 3953c46c3ac7eef31a9935427371c6f54a22f1ba ≤ v < 560b33b434e922ef97f9ff23aa2e909ef7aacd5c | CVEProject cvelistV5 (CNA) |
| Linux | Linux | 3953c46c3ac7eef31a9935427371c6f54a22f1ba ≤ v < d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e | CVEProject cvelistV5 (CNA) |
| Linux | Linux | 3953c46c3ac7eef31a9935427371c6f54a22f1ba ≤ v < a210791f33345aa87187f7d7a9f3b9b7f4a28e6d | CVEProject cvelistV5 (CNA) |
| Linux | Linux | 3953c46c3ac7eef31a9935427371c6f54a22f1ba ≤ v < 2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22 | CVEProject cvelistV5 (CNA) |
| Linux | Linux | 3953c46c3ac7eef31a9935427371c6f54a22f1ba ≤ v < 8e6214a530c03e341dc1b0a846c8f2b716b3551a | CVEProject cvelistV5 (CNA) |
References and advisories
8- https://git.kernel.org/stable/c/560b33b434e922ef97f9ff23aa2e909ef7aacd5c
- https://git.kernel.org/stable/c/21f69ac1879bb970588d5e7c12a96e6542f7c1a7
- https://git.kernel.org/stable/c/c0db3dc2ac323b6c4b76adede3b355a9daa6dea8
- https://git.kernel.org/stable/c/572fff10819dfc359298d1f774839e76a4d96f93
- https://git.kernel.org/stable/c/8e6214a530c03e341dc1b0a846c8f2b716b3551a
- https://git.kernel.org/stable/c/d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e
- https://git.kernel.org/stable/c/a210791f33345aa87187f7d7a9f3b9b7f4a28e6d
- https://git.kernel.org/stable/c/2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22
Details
- Published
- 2026-08-15
- Last updated
- 2026-10-16
- State
- Published
- Assigner (CNA)
- Linux
Exploit prediction (EPSS)
SSVC assessment (CISA)
- Automatable
- Yes
- Exploitation
- None
- Technical impact
- Partial
Weaknesses (CWE)
- —