Description (CNA)
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 (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 10d3be569243def8d92ac3722395ef5a59c504e6 before 8eb51013b6308870479a64b4a2a018697b997849; affected 10d3be569243def8d92ac3722395ef5a59c504e6 before 711bfd762bec05fb19bc3b17cbb157c39f4e66da; affected 10d3be569243def8d92ac3722395ef5a59c504e6 before 3d4e005c198dc410ad568f832bffa7569c059ff8; affected 10d3be569243def8d92ac3722395ef5a59c504e6 before 4fd2ee4ac154c204d95d8db72221446dac5af9b8; affected 10d3be569243def8d92ac3722395ef5a59c504e6 before ebe55406404f3cb28e36d2b668e2c6c05026ec29; affected 10d3be569243def8d92ac3722395ef5a59c504e6 before b8f08a94b2a4addc39249dcf9c792e786108621b; affected 10d3be569243def8d92ac3722395ef5a59c504e6 before 47eb90299e6882d6445672530dd7c51ac33ebdbd; affected 10d3be569243def8d92ac3722395ef5a59c504e6 before ce2b807f42ed5e55567b8864ab72963f90779270 |
| Linux / Linux | affected 4.7; unaffected 0 before 4.7; unaffected 5.10.270 through 5.10.*; unaffected 5.15.221 through 5.15.*; unaffected 6.1.188 through 6.1.*; unaffected 6.6.157 through 6.6.*; unaffected 6.12.110 through 6.12.*; unaffected 6.18.52 through 6.18.*; unaffected 7.2.6 through 7.2.*; unaffected 7.3 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/8eb51013b6308870479a64b4a2a018697b997849
- https://git.kernel.org/stable/c/711bfd762bec05fb19bc3b17cbb157c39f4e66da
- https://git.kernel.org/stable/c/3d4e005c198dc410ad568f832bffa7569c059ff8
- https://git.kernel.org/stable/c/4fd2ee4ac154c204d95d8db72221446dac5af9b8
- https://git.kernel.org/stable/c/ebe55406404f3cb28e36d2b668e2c6c05026ec29
- https://git.kernel.org/stable/c/b8f08a94b2a4addc39249dcf9c792e786108621b
- https://git.kernel.org/stable/c/47eb90299e6882d6445672530dd7c51ac33ebdbd
- https://git.kernel.org/stable/c/ce2b807f42ed5e55567b8864ab72963f90779270