CVE-2026-90054
Full vulnerability record from the local CVENow database.
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.
View original CVE JSON
{
"id": "CVE-2026-90054",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-09-17T17:16:53.873",
"lastModified": "2026-10-19T09:18:53.667",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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 > 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 > 1 skb and hands it to the GSO layer, which only advances th->seq\nper segment and copies urg_ptr verbatim:\n\n\t/* __tcp_retransmit_skb() */\n\tlen = cur_mss * segs;\t\t/* segs > 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 -> urgent @ 5001 (ok)\n\tseg2 seq 1001 urg_ptr 5001 -> urgent @ 6001 (wrong, +MSS)\n\tseg3 seq 2001 urg_ptr 5001 -> 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."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"net/ipv4/tcp_output.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
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"lessThan": "8eb51013b6308870479a64b4a2a018697b997849",
"versionType": "git",
"status": "affected"
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{
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"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"net/ipv4/tcp_output.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "4.7",
"status": "affected"
},
{
"version": "0",
"lessThan": "4.7",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.10.270",
"lessThanOrEqual": "5.10.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.15.221",
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"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.1.188",
"lessThanOrEqual": "6.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.157",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.110",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.52",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2.6",
"lessThanOrEqual": "7.2.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.3",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {},
"references": [
{
"url": "https://git.kernel.org/stable/c/3d4e005c198dc410ad568f832bffa7569c059ff8",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
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}