CVE-2026-53181 vsock/vmci: fix sk_ack_backlog leak on failed handshake
A resource leak in the Linux kernel's vsock/vmci module allows attackers to cause a permanent denial of service by exhausting the connection backlog.
- 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-2026-53181?
CVE-2026-53181 is a medium-severity denial of service 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:
vsock/vmci: fix sk_ack_backlog leak on failed handshake
When vmci_transport_recv_connecting_server() returns an error, vmci_transport_recv_listen() calls vsock_remove_pending() but never calls sk_acceptq_removed(). This leaves sk_ack_backlog incremented permanently.
Repeated handshake failures (malformed packets, queue pair alloc failure, event subscribe failure) cause sk_ack_backlog to climb toward sk_max_ack_backlog. Once it reaches the limit the listener permanently refuses all new connections with -ECONNREFUSED, a silent denial of service requiring a process restart to recover.
The two existing sk_acceptq_removed() calls in af_vsock.c do not cover this path: line 764 checks vsock_is_pending() which returns false after vsock_remove_pending(), and line 1889 is only reached on successful accept().
Fix by balancing sk_acceptq_added() with sk_acceptq_removed() on the error path.
Weakness: CWE-401
Which versions are affected by CVE-2026-53181?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53181?
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-2026-53181 being exploited?
There is no known exploitation of CVE-2026-53181 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-90627, BELL-CVE-2026-53181, DEBIAN-CVE-2026-53181, GHSA-6gq6-hxjh-9grq, ROOT-OS-DEBIAN-11-CVE-2026-53181, ROOT-OS-DEBIAN-12-CVE-2026-53181 and 3 more.