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CVE-2026-90054

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

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, and 2 more
None on Exploit-DB, Metasploit or GitHub

Summary

In 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.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 10d3be569243def8d92ac3722395ef5a59c504e6 · fixed in 8eb51013b6308870479a64b4a2a018697b997849; From 10d3be569243def8d92ac3722395ef5a59c504e6 · fixed in 711bfd762bec05fb19bc3b17cbb157c39f4e66da; From 10d3be569243def8d92ac3722395ef5a59c504e6 · fixed in 3d4e005c198dc410ad568f832bffa7569c059ff8; From 10d3be569243def8d92ac3722395ef5a59c504e6 · fixed in 4fd2ee4ac154c204d95d8db72221446dac5af9b8; From 10d3be569243def8d92ac3722395ef5a59c504e6 · fixed in ebe55406404f3cb28e36d2b668e2c6c05026ec29; From 10d3be569243def8d92ac3722395ef5a59c504e6 · fixed in b8f08a94b2a4addc39249dcf9c792e786108621b; From 10d3be569243def8d92ac3722395ef5a59c504e6 · fixed in 47eb90299e6882d6445672530dd7c51ac33ebdbd; From 10d3be569243def8d92ac3722395ef5a59c504e6 · fixed in ce2b807f42ed5e55567b8864ab72963f90779270

  • Linux Linux

    4.7

  • KernelLinux

    From 4.7.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6

References 8

git.kernel.org