CVE-2026-53236: tcp: restrict SO_ATTACH_FILTER to priv users
In the Linux kernel, the following vulnerability has been resolved:
tcp: restrict SOATTACHFILTER to priv users
This patch restricts the use of SOATTACHFILTER (cBPF) on TCP sockets to users with CAPNETADMIN capability.
This blocks potential side-channel attack where an unprivileged application attaches a filter to leak TCP sequence/acknowledgment numbers.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.6.143.1-1 - Configuration
Update the kernel so that SO_ATTACH_FILTER (cBPF) can only be used by privileged users with CAP_NET_ADMIN on TCP sockets, preventing unprivileged apps from attaching filters that could leak TCP sequence/acknowledgment numbers.
Linux kernel TCP SO_ATTACH_FILTER (cBPF) usage = Restrict to users with CAP_NET_ADMIN (privileged) capability
Event History
Frequently Asked Questions
What is the severity of CVE-2026-53236?
CVE-2026-53236 has a risk rating of 27.
How do I fix CVE-2026-53236?
To mitigate CVE-2026-53236, ensure that only users with CAP_NET_ADMIN capability can use SO_ATTACH_FILTER on TCP sockets.
What systems are affected by CVE-2026-53236?
CVE-2026-53236 affects the Linux kernel that implements TCP sockets.
What is the main risk associated with CVE-2026-53236?
The main risk of CVE-2026-53236 is the potential for unprivileged applications to exploit side-channel attacks via TCP socket filters.
When was CVE-2026-53236 published?
CVE-2026-53236 was published on June 25, 2026.