CVE-2026-98255tcp: exclude old ACKs from tcp fast path
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- Not yet scored
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Received
- Record last updated
- Oct 19, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | 31770e34e43d6c8dee129bfee77e56c34e61f0e5 builds before 07cacab90290f795bad2e566790f4ba8e84cdf5f; 31770e34e43d6c8dee129bfee77e56c34e61f0e5 builds before 6eb9b697f50b73b9684e466c1e97f4ca8e947a59; from 31770e34e43d6c8dee129bfee77e56c34e61f0e5 before b86e1e5a4bbcbbccde8b7a3d3486604b581f6628; 31770e34e43d6c8dee129bfee77e56c34e61f0e5 builds before 1c8448db5cf35a13d82b0c9004ffdb49358883e7; 31770e34e43d6c8dee129bfee77e56c34e61f0e5 builds before 8309dc2cc360056aa9cd2acfbfc25930798c3b66; from 31770e34e43d6c8dee129bfee77e56c34e61f0e5 before ff037920c688ae6ca1153fec01e90e6782712455; 31770e34e43d6c8dee129bfee77e56c34e61f0e5 builds before 8205ac5ddb42a1843fa8d6a8c295b5c7f4f8c6ed; from 31770e34e43d6c8dee129bfee77e56c34e61f0e5 before f81e6c3fb06327bc49cdd6e559845293ba06a704 | CNA record |
References
- https://git.kernel.org/stable/c/07cacab90290f795bad2e566790f4ba8e84cdf5f
- https://git.kernel.org/stable/c/6eb9b697f50b73b9684e466c1e97f4ca8e947a59
- https://git.kernel.org/stable/c/b86e1e5a4bbcbbccde8b7a3d3486604b581f6628
- https://git.kernel.org/stable/c/1c8448db5cf35a13d82b0c9004ffdb49358883e7
- https://git.kernel.org/stable/c/8309dc2cc360056aa9cd2acfbfc25930798c3b66
- https://git.kernel.org/stable/c/ff037920c688ae6ca1153fec01e90e6782712455
- https://git.kernel.org/stable/c/8205ac5ddb42a1843fa8d6a8c295b5c7f4f8c6ed
- https://git.kernel.org/stable/c/f81e6c3fb06327bc49cdd6e559845293ba06a704
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.