CVE-2026-90138
UnknownSummary
In the Linux kernel, vsock_accept() checked the listener's sk_err field, causing valid incoming connections to be rejected if a stale error from an earlier failed connection attempt (e.g., self-connect returning EPROTO) remained on the socket. This led to a resource leak — the child socket created for the rejected connection was never freed on virtio and hyperv transports. The issue was resolved by removing these checks.
Risk Assessment
Organizations may experience socket resource leaks on systems using AF_VSOCK over virtio or hyperv transports, potentially leading to resource exhaustion and denial of service. Rejection of valid connections may also disrupt communication between virtual machines and the host.
Recommendation
Update the Linux kernel to a version containing the fix that removes the sk_err check in vsock_accept(). If updating is not possible, consider restricting or monitoring AF_VSOCK usage on affected transports.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: vsock: don't check the listener's sk_err in vsock_accept() Syzbot reported an issue which can be reproduced with these steps: r0 = socket(AF_VSOCK, SOCK_STREAM, 0) bind(r0, {VMADDR_CID_ANY, PORT}) connect(r0, {VMADDR_CID_LOCAL, PORT}) -> -1, EPROTO (self-connect) listen(r0, backlog) -> 0 r1 = socket(AF_VSOCK, SOCK_STREAM, 0) connect(r1, {VMADDR_CID_LOCAL, PORT}) -> 0 accept(r0) -> -1, EPROTO (stale sk_err) Basically, it creates a socket (r0) and triggers a self-connect after binding it. This self-connect fails with EPROTO because it loops back to r0 while the socket is still in the TCP_SYN_SENT state, causing it to be incorrectly dispatched to the connecting-client path. The unexpected packet type encountered there sets sk_err to EPROTO. After that, it invokes a listen() call on the same socket. This listen() call succeeds because the kernel's listening path never inspects or clears sk_err. Then, a new socket (r1) is created as a normal client and connects to r0. However, vsock_accept() rejects this incoming connection because the listener's sk_err still holds the EPROTO error from the earlier failed self-connect. This rejection causes the child socket created for r1's connection to never be freed on virtio or hyperv transports; only the VMCI transport implements pending_work to revisit and clean up a rejected socket. For a non-blocking connect(), vsock_connect() may return -EINPROGRESS immediately, and vsock_connect_timeout() can later set sk->sk_err asynchronously. Since no vsock transport ever sets sk_err on a socket while it is in TCP_LISTEN state, checking it in vsock_accept() serves no purpose and only carries forward errors left behind by earlier, unrelated connection attempts on the same socket. Remove the checks so accept() no longer rejects valid incoming connections because of a stale error, which also avoids the resource leak described above.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS