CVE-2026-31476 ksmbd: do not expire session on binding failure
A remote attacker can cause denial of service by invalidating active sessions via failed multichannel binding requests in the Linux kernel ksmbd module.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-31476?
CVE-2026-31476 is a high-severity denial of service vulnerability in Linux kernel, published on 22 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: do not expire session on binding failure
When a multichannel session binding request fails (e.g. wrong password), the error path unconditionally sets sess->state = SMB2_SESSION_EXPIRED. However, during binding, sess points to the target session looked up via ksmbd_session_lookup_slowpath() -- which belongs to another connection's user. This allows a remote attacker to invalidate any active session by simply sending a binding request with a wrong password (DoS).
Fix this by skipping session expiration when the failed request was a binding attempt, since the session does not belong to the current connection. The reference taken by ksmbd_session_lookup_slowpath() is still correctly released via ksmbd_user_session_put().
Which versions are affected by CVE-2026-31476?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31476?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-31476 being exploited?
There is no known exploitation of CVE-2026-31476 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-83210, BELL-CVE-2026-31476, DEBIAN-CVE-2026-31476, GHSA-223f-gch2-xvq3, ROOT-OS-DEBIAN-12-CVE-2026-31476, ROOT-OS-UBUNTU-2204-CVE-2026-31476 and 2 more.