{"id":"CVE-2026-90054","summary":"tcp: fix corruption of urgent data on multi-segment retransmit","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix corruption of urgent data on multi-segment retransmit\n\nOn the normal xmit path, while in urgent mode we refuse to build a\nmulti-segment TSO packet, so every segment gets its own urg_ptr:\n\n\t/* tcp_write_xmit() */\n\tlimit = mss_now;\n\tif (tso_segs \u003e 1 && !tcp_urg_mode(tp))\n\t\tlimit = tcp_mss_split_point(...);\n\nThe retransmit path has no such guard. __tcp_retransmit_skb() builds a\nsegs \u003e 1 skb and hands it to the GSO layer, which only advances th-\u003eseq\nper segment and copies urg_ptr verbatim:\n\n\t/* __tcp_retransmit_skb() */\n\tlen = cur_mss * segs;\t\t/* segs \u003e 1, no urg_mode check */\n\t...\n\t/* tcp_gso_segment(): bumps seq only, urg_ptr is copied */\n\nurg_ptr is an offset from the segment's own seq, so a copied value points\nat a different place on each segment. The receiver rebuilds the absolute\nurgent seq as seg.seq + urg_ptr, so it walks a moving urgent point instead\nof the one OOB byte:\n\n\tseg1  seq 1     urg_ptr 5001 -\u003e urgent @ 5001   (ok)\n\tseg2  seq 1001  urg_ptr 5001 -\u003e urgent @ 6001   (wrong, +MSS)\n\tseg3  seq 2001  urg_ptr 5001 -\u003e urgent @ 7001   (wrong, +2*MSS)\n\nThe real OOB byte is never pointed at, so the receiver stops splicing it\nout and delivers it as normal in-band data, corrupting the stream.\n\nGuard the retransmit length like the xmit path: keep segs = 1 while in\nurgent mode.","modified":"2026-09-19T03:46:40.830765020Z","published":"2026-09-17T16:05:39.632Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90054.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/3d4e005c198dc410ad568f832bffa7569c059ff8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/47eb90299e6882d6445672530dd7c51ac33ebdbd"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4fd2ee4ac154c204d95d8db72221446dac5af9b8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/711bfd762bec05fb19bc3b17cbb157c39f4e66da"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8eb51013b6308870479a64b4a2a018697b997849"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b8f08a94b2a4addc39249dcf9c792e786108621b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ce2b807f42ed5e55567b8864ab72963f90779270"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ebe55406404f3cb28e36d2b668e2c6c05026ec29"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90054.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90054"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"10d3be569243def8d92ac3722395ef5a59c504e6"},{"fixed":"8eb51013b6308870479a64b4a2a018697b997849"},{"fixed":"711bfd762bec05fb19bc3b17cbb157c39f4e66da"},{"fixed":"3d4e005c198dc410ad568f832bffa7569c059ff8"},{"fixed":"4fd2ee4ac154c204d95d8db72221446dac5af9b8"},{"fixed":"ebe55406404f3cb28e36d2b668e2c6c05026ec29"},{"fixed":"b8f08a94b2a4addc39249dcf9c792e786108621b"},{"fixed":"47eb90299e6882d6445672530dd7c51ac33ebdbd"},{"fixed":"ce2b807f42ed5e55567b8864ab72963f90779270"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90054.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.7.0"},{"fixed":"5.10.270"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.221"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.188"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.157"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.110"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.52"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90054.json"}}],"schema_version":"1.9.0"}