---
id: CVE-2026-90054
title: |-
  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 se…
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 se…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 10d3be569243def8d92ac3722395ef5a59c504e6 <
    8eb51013b6308870479a64b4a2a018697b997849
  - >-
    Linux >= 10d3be569243def8d92ac3722395ef5a59c504e6 <
    711bfd762bec05fb19bc3b17cbb157c39f4e66da
  - >-
    Linux >= 10d3be569243def8d92ac3722395ef5a59c504e6 <
    3d4e005c198dc410ad568f832bffa7569c059ff8
  - >-
    Linux >= 10d3be569243def8d92ac3722395ef5a59c504e6 <
    4fd2ee4ac154c204d95d8db72221446dac5af9b8
  - >-
    Linux >= 10d3be569243def8d92ac3722395ef5a59c504e6 <
    ebe55406404f3cb28e36d2b668e2c6c05026ec29
  - >-
    Linux >= 10d3be569243def8d92ac3722395ef5a59c504e6 <
    b8f08a94b2a4addc39249dcf9c792e786108621b
  - >-
    Linux >= 10d3be569243def8d92ac3722395ef5a59c504e6 <
    47eb90299e6882d6445672530dd7c51ac33ebdbd
  - >-
    Linux >= 10d3be569243def8d92ac3722395ef5a59c504e6 <
    ce2b807f42ed5e55567b8864ab72963f90779270
  - Linux 4.7
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:16:53.873'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-90054'
references:
  - url: 'https://git.kernel.org/stable/c/3d4e005c198dc410ad568f832bffa7569c059ff8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/47eb90299e6882d6445672530dd7c51ac33ebdbd'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4fd2ee4ac154c204d95d8db72221446dac5af9b8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/711bfd762bec05fb19bc3b17cbb157c39f4e66da'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8eb51013b6308870479a64b4a2a018697b997849'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b8f08a94b2a4addc39249dcf9c792e786108621b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ce2b807f42ed5e55567b8864ab72963f90779270'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ebe55406404f3cb28e36d2b668e2c6c05026ec29'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.903Z'
epss: 0.0022
epssPercentile: 0.11101
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.