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".
Fix
Nothing published yet: no patch, vendor advisory or mitigation reference on NVD, no vendor advisory in the News for this CVE, not in CISA's KEV, no fixed package version. BaselineWatch does not guess at one.
Change history 1
- First seenCVSS 7.5NVD modified 2026-10-16 19:17
Affected (CPE criteria) 0
NVD has not attached CPE configurations yet.
References 8
- https://git.kernel.org/stable/c/21f69ac1879bb970588d5e7c12a96e6542f7c1a7
- https://git.kernel.org/stable/c/2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22
- https://git.kernel.org/stable/c/560b33b434e922ef97f9ff23aa2e909ef7aacd5c
- https://git.kernel.org/stable/c/572fff10819dfc359298d1f774839e76a4d96f93
- https://git.kernel.org/stable/c/8e6214a530c03e341dc1b0a846c8f2b716b3551a
- https://git.kernel.org/stable/c/a210791f33345aa87187f7d7a9f3b9b7f4a28e6d
- https://git.kernel.org/stable/c/c0db3dc2ac323b6c4b76adede3b355a9daa6dea8
- https://git.kernel.org/stable/c/d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e