tcp: challenge ACK for non-exact RST in SYN-RECEIVED

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Summary

CVECVE-2026-68118
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-10 13:19:56 UTC
Updated2026-08-10 13:19:56 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: tcp: challenge ACK for non-exact RST in SYN-RECEIVED The SYN-RECEIVED request-socket path in tcp_check_req() accepts an in-window RST without requiring SEG.SEQ to exactly match RCV.NXT. A non-exact RST therefore removes the request instead of eliciting a challenge ACK. RFC 9293 section 3.10.7.4 applies the RFC 5961 reset check in SYN-RECEIVED: an exact RST resets the connection, while a non-exact in-window RST must trigger a challenge ACK and be dropped. Apply that check before the ACK-field validation, following the RFC sequence-number, RST, then ACK processing order. Factor the per-netns challenge ACK quota out of tcp_send_challenge_ack() so request sockets can share it. Use the request socket's send_ack() callback and its own out-of-window ACK timestamp to send and rate-limit the response.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 282f23c6ee343126156dd41218b22ece96d747e3 234f9ffbd9b2c1b24ec67200ea3cff07401bec48 git Not specified
CNA Linux Linux affected 282f23c6ee343126156dd41218b22ece96d747e3 22cec809b048495310f206d9abbcdbbfbdce3ae3 git Not specified
CNA Linux Linux affected 282f23c6ee343126156dd41218b22ece96d747e3 a28c4fcbf774e23b4779cae468e3497a5ad1f4a1 git Not specified
CNA Linux Linux affected 86791bbfe5ed7b275be040cfeff049a1624af1b7 git Not specified
CNA Linux Linux affected 61f69dc4e40e41b0018f00fa4aeb23d3239556fb git Not specified
CNA Linux Linux affected 34fb350281ced2a72707a5c0064f69992d440edb git Not specified
CNA Linux Linux affected 3.0.58 3.1 semver Not specified
CNA Linux Linux affected 3.2.37 3.3 semver Not specified
CNA Linux Linux affected 3.4.25 3.5 semver Not specified
CNA Linux Linux affected 3.6 Not specified
CNA Linux Linux unaffected 3.6 semver Not specified
CNA Linux Linux unaffected 6.18.42 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.6 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc5 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a28c4fcbf774e23b4779cae468e3497a5ad1f4a1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/22cec809b048495310f206d9abbcdbbfbdce3ae3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/234f9ffbd9b2c1b24ec67200ea3cff07401bec48 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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