CVE-2026-90054: Linux Vulnerability

Description

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.

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 10d3be569243def8d92ac3722395ef5a59c504e6, < 8eb51013b6308870479a64b4a2a018697b997849; >= 10d3be569243def8d92ac3722395ef5a59c504e6, < 711bfd762bec05fb19bc3b17cbb157c39f4e66da; >= 10d3be569243def8d92ac3722395ef5a59c504e6, < 3d4e005c198dc410ad568f832bffa7569c059ff8; >= 10d3be569243def8d92ac3722395ef5a59c504e6, < 4fd2ee4ac154c204d95d8db72221446dac5af9b8; >= 10d3be569243def8d92ac3722395ef5a59c504e6, < ebe55406404f3cb28e36d2b668e2c6c05026ec29; >= 10d3be569243def8d92ac3722395ef5a59c504e6, < b8f08a94b2a4addc39249dcf9c792e786108621b; >= 10d3be569243def8d92ac3722395ef5a59c504e6, < 47eb90299e6882d6445672530dd7c51ac33ebdbd; >= 10d3be569243def8d92ac3722395ef5a59c504e6, < ce2b807f42ed5e55567b8864ab72963f90779270
Linux	Linux	4.7

References

Timeline

Published: Sep 17, 2026
Last Modified: Sep 17, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-90054?

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.

How severe is CVE-2026-90054?

Severity scoring for CVE-2026-90054 is pending analysis.

How do I fix CVE-2026-90054?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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