{"id":"CVE-2026-98374","summary":"tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()\n\nWhen tcp_send_synack() replaces the cloned SYN skb at the head of the\nretransmit queue with a copy, it frees the original with\ntcp_rtx_queue_unlink_and_free() and only repairs tp-\u003ehighest_sack.\ntp-\u003eretransmit_skb_hint keeps pointing at the freed\nskbuff_fclone_cache object.\n\nThe dangling hint is read in tcp_verify_retransmit_hint() and used as\nthe root of the rbtree walk in tcp_xmit_retransmit_queue().  An\nunprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with\nan attacker-supplied ICMP fragmentation-needed message, after which a\nsimultaneous open frees the armed SYN skb:\n\n  BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n  Read of size 4 at addr ffff88800604d928 by task swapper/1/0\n  Call Trace:\n   tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n   tcp_simple_retransmit (net/ipv4/tcp_input.c:3158)\n   tcp_v4_err (net/ipv4/tcp_ipv4.c:587)\n\nSync the hint to the copy.","modified":"2026-10-08T02:52:58.340591968Z","published":"2026-10-07T13:01:48.600Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98374.json","cna_assigner":"Linux"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98374.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98374"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c31b70c9968fe9c4194d1b5d06d07596a3b680de"},{"fixed":"fad6d429651e748365e93ca54645accc212f0018"},{"fixed":"c5b4da1f403a658c1c19766be2b426003ada419f"},{"fixed":"71d45049b0d631dfdbf3c65305f7fca676de023b"},{"fixed":"e3ea71cb1408a013ed4e8a757b815f1a919324bd"},{"fixed":"631aa4cb45099f09e9385dd786bd291c6270bfc4"},{"fixed":"0f87720c7e4bcab07c24888b3cf12bfe857bb90e"},{"fixed":"fe99bbeee5c5dbd3abc30721a8079ced59649d97"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98374.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.222"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.189"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.158"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.112"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.55"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98374.json"}}],"schema_version":"1.9.0"}