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

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-25 · updated 2026-10-15

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.

Affected products

Linux kernel: from 5.3 before 5.10.259; from 5.11 before 5.15.210; from 5.16 before 6.1.176; from 6.2 before 6.6.143; from 6.7 before 6.12.94; from 6.13 before 6.18.36 — fixed in 5.10.259, 5.15.210, 6.1.176, 6.12.94, 6.18.36, 6.6.143

How to fix

Upgrade to a fixed version: Linux kernel 5.10.259, 5.15.210, 6.1.176, 6.12.94. Check the vendor advisory for mitigations.

References

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