CVE-2026-53236 tcp: restrict SO_ATTACH_FILTER to priv users
An unprivileged user can attach a BPF filter to TCP sockets to leak sequence and acknowledgment numbers via a side-channel attack.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53236?
CVE-2026-53236 is a medium-severity vulnerability in Linux kernel, published on 25 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
tcp: restrict SO_ATTACH_FILTER to priv users
This patch restricts the use of SO_ATTACH_FILTER (cBPF) on TCP sockets to users with CAP_NET_ADMIN capability.
This blocks potential side-channel attack where an unprivileged application attaches a filter to leak TCP sequence/acknowledgment numbers.
Which versions are affected by CVE-2026-53236?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53236?
Apply the vendor's patch.
Is CVE-2026-53236 being exploited?
There is no known exploitation of CVE-2026-53236 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-90572, BELL-CVE-2026-53236, DEBIAN-CVE-2026-53236, GHSA-jmmv-2hp7-p7g5, ROOT-OS-DEBIAN-11-CVE-2026-53236, ROOT-OS-DEBIAN-12-CVE-2026-53236 and 3 more.