tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98374
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-07 13:17:23 UTC
Updated2026-10-24 14:16:39 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack() When tcp_send_synack() replaces the cloned SYN skb at the head of the retransmit queue with a copy, it frees the original with tcp_rtx_queue_unlink_and_free() and only repairs tp->highest_sack. tp->retransmit_skb_hint keeps pointing at the freed skbuff_fclone_cache object. The dangling hint is read in tcp_verify_retransmit_hint() and used as the root of the rbtree walk in tcp_xmit_retransmit_queue(). An unprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with an attacker-supplied ICMP fragmentation-needed message, after which a simultaneous open frees the armed SYN skb: BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316) Read of size 4 at addr ffff88800604d928 by task swapper/1/0 Call Trace: tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316) tcp_simple_retransmit (net/ipv4/tcp_input.c:3158) tcp_v4_err (net/ipv4/tcp_ipv4.c:587) Sync the hint to the copy.

Risk And Classification

Primary CVSS: v3.1 8.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.8HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
3.1CNADECLARED8.8HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected c31b70c9968fe9c4194d1b5d06d07596a3b680de fad6d429651e748365e93ca54645accc212f0018 git Not specified
CNA Linux Linux affected c31b70c9968fe9c4194d1b5d06d07596a3b680de c5b4da1f403a658c1c19766be2b426003ada419f git Not specified
CNA Linux Linux affected c31b70c9968fe9c4194d1b5d06d07596a3b680de 71d45049b0d631dfdbf3c65305f7fca676de023b git Not specified
CNA Linux Linux affected c31b70c9968fe9c4194d1b5d06d07596a3b680de e3ea71cb1408a013ed4e8a757b815f1a919324bd git Not specified
CNA Linux Linux affected c31b70c9968fe9c4194d1b5d06d07596a3b680de 631aa4cb45099f09e9385dd786bd291c6270bfc4 git Not specified
CNA Linux Linux affected c31b70c9968fe9c4194d1b5d06d07596a3b680de 0f87720c7e4bcab07c24888b3cf12bfe857bb90e git Not specified
CNA Linux Linux affected c31b70c9968fe9c4194d1b5d06d07596a3b680de fe99bbeee5c5dbd3abc30721a8079ced59649d97 git Not specified
CNA Linux Linux affected 5.11 Not specified
CNA Linux Linux unaffected 5.11 semver Not specified
CNA Linux Linux unaffected 5.15.222 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.189 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.158 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.112 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.55 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.9 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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