Discovery API Icon
Discovery API
Security Advisory Icon
Security Advisory
Package Manager Icon
Package Manager
Alpaquita LinuxStreamSecurity Advisory
Search Cve

CVE-2026-63913

Published: July 22, 2026Last modified: July 22, 2026

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check An unintended behavior in the TCP conntrack state machine allows a connection to be forced into the CLOSE state using an RST packet with an invalid sequence number. Specifically, after a SYN packet is observed, an RST with an invalid SEQ can transition the conntrack entry to TCP_CONNTRACK_CLOSE, regardless of whether the RST corresponds to the expected reply direction. The relevant code path assumes the RST is a response to an outgoing SYN, but does not validate packet direction or ensure that a matching SYN was actually sent in the opposite direction. As a result, a crafted packet sequence consisting of a SYN followed by an invalid-sequence RST can prematurely terminate an active NAT entry. This makes connection teardown easier than intended. So, tighten the state transition logic to ensure that RST-triggered CLOSE transitions only occur when the RST is a valid response to a previously observed SYN in the correct direction.

Severity score breakdown

ParameterValue
Base score8.2
Attack VectorNETWORK
Attack complexityLOW
Privileges requiredNONE
User interactionNONE
ScopeUNCHANGED
ConfidentialityNONE
Integrity impactLOW
Availability impactHIGH
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Status

ProductReleasePackageStatus
Alpaquita Linux23 LTSlinux-ltsFixed (6.1.177-r0)
25 LTSlinux-ltsFixed (6.12.95-r0)
Streamlinux-ltsFixed (6.18.35-r1)

References

ON THIS PAGE