{"id":"CVE-2026-98374","published":"2026-10-07T13:17:23.023","lastModified":"2026-10-07T13:17:23.023","description":"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->highest_sack.\ntp->retransmit_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.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e","tags":[]},{"url":"https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4","tags":[]},{"url":"https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b","tags":[]},{"url":"https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f","tags":[]},{"url":"https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd","tags":[]},{"url":"https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018","tags":[]},{"url":"https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}