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CVE-2026-98255

unscored Published
NVD · CVE.org

In the Linux kernel, the following vulnerability has been resolved: tcp: exclude old ACKs from tcp fast path Exclude old ACKs before SND.UNA from the tcp fast path as well as ACKs after SND.NXT. Such ACKs will fall through to the slow path, where tcp_ack() performs the appropriate validation and challenge ACK handling according to RFC5961 and Commit 3d501dd326fb1c7 ("tcp: do not accept ACK of bytes we never sent"). This prevents old ACKs from being accepted or modifying connection state as part of the fast path before appropriate ACK validation is applied. In particular, this prevents payload carried by a segment with an excessively old ACK from advancing RCV.NXT before the ACK is rejected.

Fix

Microsoft's update · Critical

  • Release Notes — azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 · build 6.6.158.1-1

From the 2026-Oct release note of Microsoft's Security Update Guide, revised 2026-10-29.

Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.

Change history 2

  1. StatusReceived → PublishedNVD modified 2026-10-19 09:16
  2. First seenunscoredNVD modified 2026-10-19 10:18

Affected (CPE criteria) 0

NVD has not attached CPE configurations yet.

References 8