VulnerabilityPublished 25 Jun 2026Updated 6 Nov 2026

CVE-2026-53269: Linux kernel · netfilter: synproxy: add mutex to guard hook reference counting

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in fbf0591275f50eae5733c3d7a8cd6c1e79933ffa : update Linux kernel when convenient.

Data as of 6 Nov 2026, 16:49 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in fbf0591275f50eae5733c3d7a8cd6c1e79933ffa, debc57b83d5b323df74bf010c8d50fe26ad2ed6b, aaf80701dc2f7a48fe543961e21f8ca3924d587c +5

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ ad49d86e07a497e834cb06f2b151dccd75f8e148, < fbf0591275f50eae5733c3d7a8cd6c1e79933ffa	Fixed in fbf0591275f50eae5733c3d7a8cd6c1e79933ffa
LinuxLinux	Affected ≥ ad49d86e07a497e834cb06f2b151dccd75f8e148, < debc57b83d5b323df74bf010c8d50fe26ad2ed6b	Fixed in debc57b83d5b323df74bf010c8d50fe26ad2ed6b
LinuxLinux	Affected ≥ ad49d86e07a497e834cb06f2b151dccd75f8e148, < aaf80701dc2f7a48fe543961e21f8ca3924d587c	Fixed in aaf80701dc2f7a48fe543961e21f8ca3924d587c
LinuxLinux	Affected ≥ ad49d86e07a497e834cb06f2b151dccd75f8e148, < 640441348258220e78daed40528b85b8afcedab6	Fixed in 640441348258220e78daed40528b85b8afcedab6
LinuxLinux	Affected ≥ ad49d86e07a497e834cb06f2b151dccd75f8e148, < 56ffbe3a08c01dcdb0d6adee9ce1e535bfb3b389	Fixed in 56ffbe3a08c01dcdb0d6adee9ce1e535bfb3b389
LinuxLinux	Affected ≥ ad49d86e07a497e834cb06f2b151dccd75f8e148, < 2fcba19caaeb2a33017459d3430f057967bb91b6	Fixed in 2fcba19caaeb2a33017459d3430f057967bb91b6

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: synproxy: add mutex to guard hook reference counting As the synproxy infrastructure register netfilter hooks on-demand when a user adds the first iptables target or nftables expression, if done concurrently they can race each other. Introduce a mutex to serialize the refcount control blocks access from both frontends. While a per namespace mutex might be more efficient, it is not needed for target/expression like SYNPROXY.

References

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