tcp: fix corruption of urgent data on multi-segment retransmit

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-90054
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-17 17:16:53 UTC
Updated2026-09-17 17:16:53 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: tcp: fix corruption of urgent data on multi-segment retransmit On the normal xmit path, while in urgent mode we refuse to build a multi-segment TSO packet, so every segment gets its own urg_ptr: /* tcp_write_xmit() */ limit = mss_now; if (tso_segs > 1 && !tcp_urg_mode(tp)) limit = tcp_mss_split_point(...); The retransmit path has no such guard. __tcp_retransmit_skb() builds a segs > 1 skb and hands it to the GSO layer, which only advances th->seq per segment and copies urg_ptr verbatim: /* __tcp_retransmit_skb() */ len = cur_mss * segs; /* segs > 1, no urg_mode check */ ... /* tcp_gso_segment(): bumps seq only, urg_ptr is copied */ urg_ptr is an offset from the segment's own seq, so a copied value points at a different place on each segment. The receiver rebuilds the absolute urgent seq as seg.seq + urg_ptr, so it walks a moving urgent point instead of the one OOB byte: seg1 seq 1 urg_ptr 5001 -> urgent @ 5001 (ok) seg2 seq 1001 urg_ptr 5001 -> urgent @ 6001 (wrong, +MSS) seg3 seq 2001 urg_ptr 5001 -> urgent @ 7001 (wrong, +2*MSS) The real OOB byte is never pointed at, so the receiver stops splicing it out and delivers it as normal in-band data, corrupting the stream. Guard the retransmit length like the xmit path: keep segs = 1 while in urgent mode.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 10d3be569243def8d92ac3722395ef5a59c504e6 8eb51013b6308870479a64b4a2a018697b997849 git Not specified
CNA Linux Linux affected 10d3be569243def8d92ac3722395ef5a59c504e6 711bfd762bec05fb19bc3b17cbb157c39f4e66da git Not specified
CNA Linux Linux affected 10d3be569243def8d92ac3722395ef5a59c504e6 3d4e005c198dc410ad568f832bffa7569c059ff8 git Not specified
CNA Linux Linux affected 10d3be569243def8d92ac3722395ef5a59c504e6 4fd2ee4ac154c204d95d8db72221446dac5af9b8 git Not specified
CNA Linux Linux affected 10d3be569243def8d92ac3722395ef5a59c504e6 ebe55406404f3cb28e36d2b668e2c6c05026ec29 git Not specified
CNA Linux Linux affected 10d3be569243def8d92ac3722395ef5a59c504e6 b8f08a94b2a4addc39249dcf9c792e786108621b git Not specified
CNA Linux Linux affected 10d3be569243def8d92ac3722395ef5a59c504e6 47eb90299e6882d6445672530dd7c51ac33ebdbd git Not specified
CNA Linux Linux affected 10d3be569243def8d92ac3722395ef5a59c504e6 ce2b807f42ed5e55567b8864ab72963f90779270 git Not specified
CNA Linux Linux affected 4.7 Not specified
CNA Linux Linux unaffected 4.7 semver Not specified
CNA Linux Linux unaffected 5.10.270 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.221 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.188 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.157 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.110 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.52 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/ebe55406404f3cb28e36d2b668e2c6c05026ec29 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/711bfd762bec05fb19bc3b17cbb157c39f4e66da 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/47eb90299e6882d6445672530dd7c51ac33ebdbd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8eb51013b6308870479a64b4a2a018697b997849 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3d4e005c198dc410ad568f832bffa7569c059ff8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4fd2ee4ac154c204d95d8db72221446dac5af9b8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b8f08a94b2a4addc39249dcf9c792e786108621b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ce2b807f42ed5e55567b8864ab72963f90779270 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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