CVE Catalog

CVE-2026-98255

Low risk· EPSS 8%
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.18%

8th percentile - higher than 8% of all known CVEs

Summary

In the Linux kernel, in TCP code, old ACKs (before SND.UNA) are excluded from the fast path and directed to the slow path, where they are properly validated according to RFC5961. This prevents acceptance of old ACKs and modification of connection state before validation.

Risk Assessment

The vulnerability could allow an attacker to manipulate TCP connection state, potentially leading to unauthorized data injection or off-path attacks.

Recommendation

Update the kernel to a version with the fix that excludes old ACKs from the fast path.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS