CVE-2026-90138 vsock: don't check the listener's sk_err in vsock_accept()
A logic error in the Linux kernel vsock implementation causes resource leaks and connection rejections, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90138?
CVE-2026-90138 is a denial of service vulnerability in Linux, published on 17 Sep 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: 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.
Which versions are affected by CVE-2026-90138?
How do I fix CVE-2026-90138?
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-2026-90138 being exploited?
There is no known exploitation of CVE-2026-90138 in the wild and no public exploit code.
Sources
Also known as AZL-101975, BELL-CVE-2026-90138, DEBIAN-CVE-2026-90138, GHSA-r47p-87c6-4p5v, UBUNTU-CVE-2026-90138.