CVE-2026-53181
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk8th percentile — higher than 8% of all known CVEs
Summary
In the Linux kernel, a leak of the sk_ack_backlog counter was found in the vsock/vmci driver during a failed handshake. This causes the counter to increase permanently, eventually blocking all new connections when the limit is reached.
Risk Assessment
The organization is exposed to a silent denial of service (DoS) when repeated handshake failures occur. Recovery requires restarting the listening process.
Recommendation
Apply the Linux kernel patch addressing CVE-2026-53181 immediately. Update to a kernel version containing the fix commit.
Original NVD description (English source)
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.