In the Linux kernel, the following vulnerability has been resolved: netfilter: synproxy: add mutex to guard hook reference counting As the synproxy… (CVE-2026-53269)

The vulnerability in the Linux kernel's netfilter synproxy component involves a race condition during concurrent registration of netfilter hooks when users add the first iptables target or nftables expression. Without proper synchronization, concurrent operations could corrupt reference counting, potentially leading to denial of service. The patch adds a mutex to serialize access to the reference count control blocks, ensuring thread-safe updates and preventing race conditions in the synproxy infrastructure.

The vulnerability does not impact confidentiality or integrity but can cause availability issues due to race conditions in reference counting, potentially leading to denial of service. The CVSS score of 5.5 (medium severity) reflects this impact profile.

A fix has been implemented by adding a mutex to guard the hook reference counting in the synproxy infrastructure of the Linux kernel. Users should apply the official kernel updates that include this patch to remediate the vulnerability. Patch status is not explicitly confirmed in the provided data; therefore, check the vendor advisory or Linux kernel release notes for the specific fixed versions and update accordingly.