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CVE-2026-98255

Unknown

Last modified

CVE-2026-98255 is a vulnerability of currently unknown severity. 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..

Description

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.

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 31770e34e43d6c8dee129bfee77e56c34e61f0e5, < 07cacab90290f795bad2e566790f4ba8e84cdf5f; >= 31770e34e43d6c8dee129bfee77e56c34e61f0e5, < 6eb9b697f50b73b9684e466c1e97f4ca8e947a59; >= 31770e34e43d6c8dee129bfee77e56c34e61f0e5, < b86e1e5a4bbcbbccde8b7a3d3486604b581f6628; >= 31770e34e43d6c8dee129bfee77e56c34e61f0e5, < 1c8448db5cf35a13d82b0c9004ffdb49358883e7; >= 31770e34e43d6c8dee129bfee77e56c34e61f0e5, < 8309dc2cc360056aa9cd2acfbfc25930798c3b66; >= 31770e34e43d6c8dee129bfee77e56c34e61f0e5, < ff037920c688ae6ca1153fec01e90e6782712455; >= 31770e34e43d6c8dee129bfee77e56c34e61f0e5, < 8205ac5ddb42a1843fa8d6a8c295b5c7f4f8c6ed; >= 31770e34e43d6c8dee129bfee77e56c34e61f0e5, < f81e6c3fb06327bc49cdd6e559845293ba06a704
LinuxLinux4.14

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-98255?
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.
How severe is CVE-2026-98255?
Severity scoring for CVE-2026-98255 is pending analysis.
How do I fix CVE-2026-98255?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST