tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF) (Linux Linux)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.72 % · percentile 54 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- Linux
- NVD status
- Received
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".
References
- 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
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | Linux |
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | NVD · 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Secondary) |
European references
- ENISA EUVD · EUVD-2026-59401
- GCVE · GCVE-0-2026-72502
CERT-FR advisories
- CERTFR-2026-AVI-1385 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
- CERTFR-2026-AVI-1333 — Multiples vulnérabilités dans le noyau Linux d'Ubuntu · cert.ssi.gouv.fr
- CERTFR-2026-AVI-1286 — Multiples vulnérabilités dans le noyau Linux d'Ubuntu · cert.ssi.gouv.fr
- CERTFR-2026-AVI-1255 — Multiples vulnérabilités dans le noyau Linux de SUSE · cert.ssi.gouv.fr
- CERTFR-2026-AVI-1231 — Multiples vulnérabilités dans le noyau Linux de SUSE · cert.ssi.gouv.fr
- CERTFR-2026-AVI-1202 — Multiples vulnérabilités dans le noyau Linux de SUSE · cert.ssi.gouv.fr
- CERTFR-2026-AVI-1164 — Multiples vulnérabilités dans le noyau Linux de SUSE · cert.ssi.gouv.fr
Affected products
| Product | Versions |
|---|---|
| Linux · Linux | affected 3953c46c3ac7eef31a9935427371c6f54a22f1ba < 560b33b434e922ef97f9ff23aa2e909ef7aacd5c ; affected 3953c46c3ac7eef31a9935427371c6f54a22f1ba < 21f69ac1879bb970588d5e7c12a96e6542f7c1a7 ; affected 3953c46c3ac7eef31a9935427371c6f54a22f1ba < c0db3dc2ac323b6c4b76adede3b355a9daa6dea8 ; affected 3953c46c3ac7eef31a9935427371c6f54a22f1ba < 572fff10819dfc359298d1f774839e76a4d96f93 ; affected 3953c46c3ac7eef31a9935427371c6f54a22f1ba < 8e6214a530c03e341dc1b0a846c8f2b716b3551a ; affected 3953c46c3ac7eef31a9935427371c6f54a22f1ba < d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e |
| Linux · Linux | affected 4.8 ; unaffected 0 < 4.8 ; unaffected 5.10.261 ≤ 5.10.* ; unaffected 5.15.212 ≤ 5.15.* ; unaffected 6.1.178 ≤ 6.1.* ; unaffected 6.6.145 ≤ 6.6.* |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |