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CVE-2025-40320

9.8 · CRITICAL

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix potential cfid UAF in smb2_query_info_compound When smb2_query_info_compound() retries, a previously allocated…

Published Dec 8, 2025EPSS 0.42%

Overview

CVE-2025-40320 is a critical-severity vulnerability. It was published on December 8, 2025 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix potential cfid UAF in smb2_query_info_compound

When smb2_query_info_compound() retries, a previously allocated cfid may

have been freed in the first attempt.

Because cfid wasn't reset on replay, later cleanup could act on a stale

pointer, leading to a potential use-after-free.

Reinitialize cfid to NULL under the replay label.

Example trace (trimmed):

refcount_t: underflow; use-after-free.

WARNING: CPU: 1 PID: 11224 at ../lib/refcount.c:28 refcount_warn_saturate+0x9c/0x110

[...]

RIP: 0010:refcount_warn_saturate+0x9c/0x110

[...]

Call Trace:

<TASK>

smb2_query_info_compound+0x29c/0x5c0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]

? step_into+0x10d/0x690

? __legitimize_path+0x28/0x60

smb2_queryfs+0x6a/0xf0 [cifs f90b72658819bd21c94769b6a652029a07a7172f]

smb311_queryfs+0x12d/0x140 [cifs f90b72658819bd21c94769b6a652029a07a7172f]

? kmem_cache_alloc+0x18a/0x340

? getname_flags+0x46/0x1e0

cifs_s

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/327f89c21601ebb7889f8c97754b76f08ce95a0cRefgit.kernel.org/stable/c/5c76f9961c170552c1d07c830b5e145475151600Refgit.kernel.org/stable/c/939c4e33005e2a56ea8fcedddf0da92df864bd3bRefgit.kernel.org/stable/c/b556c278d43f4707a9073ca74d55581b4f279806

How CyberStrike helps

Frequently asked questions

What is CVE-2025-40320?

CVE-2025-40320 is a critical-severity vulnerability. It was published on December 8, 2025 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2025-40320?

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2025-40320?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-40320?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-40320 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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