{"id":"CVE-2026-72502","summary":"tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF)","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF)\n\nWhen MTU is large, ip6_default_advmss() can return IPV6_MAXPLEN (65535).\nThis is interpreted by TCP as mss_clamp, allowing the MSS to reach 65535.\n\nHowever, 0xFFFF is also used as a magic value GSO_BY_FRAGS in the kernel.\nIf a TCP packet with gso_size=0xFFFF is passed to skb_segment(), it will\nbe mistakenly treated as GSO_BY_FRAGS, leading to a NULL pointer\ndereference because local TCP packets do not use frag_list.\n\nFix this by returning min(IPV6_MAXPLEN, GSO_BY_FRAGS - 1) (65534) from\nip6_default_advmss() when MTU is large.\n\nAlso update the stale comment in ip6_default_advmss() which suggested\nthat IPV6_MAXPLEN is returned to mean \"any MSS\".","modified":"2026-08-18T03:56:27.441923771Z","published":"2026-08-15T05:57:33.647Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72502.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/21f69ac1879bb970588d5e7c12a96e6542f7c1a7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22"},{"type":"WEB","url":"https://git.kernel.org/stable/c/560b33b434e922ef97f9ff23aa2e909ef7aacd5c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/572fff10819dfc359298d1f774839e76a4d96f93"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8e6214a530c03e341dc1b0a846c8f2b716b3551a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a210791f33345aa87187f7d7a9f3b9b7f4a28e6d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c0db3dc2ac323b6c4b76adede3b355a9daa6dea8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72502.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72502"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3953c46c3ac7eef31a9935427371c6f54a22f1ba"},{"fixed":"560b33b434e922ef97f9ff23aa2e909ef7aacd5c"},{"fixed":"21f69ac1879bb970588d5e7c12a96e6542f7c1a7"},{"fixed":"c0db3dc2ac323b6c4b76adede3b355a9daa6dea8"},{"fixed":"572fff10819dfc359298d1f774839e76a4d96f93"},{"fixed":"8e6214a530c03e341dc1b0a846c8f2b716b3551a"},{"fixed":"d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e"},{"fixed":"a210791f33345aa87187f7d7a9f3b9b7f4a28e6d"},{"fixed":"2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72502.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.8.0"},{"fixed":"5.10.261"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.212"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.145"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.97"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.40"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72502.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}