CVE-2025-40320Critical· 9.8▾ Midnight

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 a…

▾ Midnight zone — Critical, or high with PoC / in-the-wild

Depth score54/ 100 · Moderate

impact 53.9 · likelihood 0.1 · exploitation 0

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Proof of concept

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Published

Dec 8, 2025

Updated

Oct 15, 2026

CVSS

9.8

Vendor

Linux

Product

Linux

CWE

—

Depth score

54 · Moderate

EPSS

0.42% · p36

Platforms

—

Source

NVD

Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA SSVC

decided 2026-10-15

Exploitation: none
Automatable: yes
Technical impact: total

Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.

EPSS history

Exploit-prediction probability, daily snapshots since Oct 14.

0.4% → 0.4%

Timeline

Disclosure to exploitation, from the record and what we observed since indexing it.

3 events · 311 days

Dec 8, 2025Published
Disclosed via NVD
Oct 14, 2026EPSS first tracked
0.4%
Oct 15, 2026Record revised
Last analysed / modified upstream

Linux #nvd #cve.org

Affected

Linux >= 433042a91f9373241307725b52de573933ffedbf < 939c4e33005e2a56ea8fcedddf0da92df864bd3b
Linux >= 4f1fffa2376922f3d1d506e49c0fd445b023a28e < 327f89c21601ebb7889f8c97754b76f08ce95a0c
Linux >= 4f1fffa2376922f3d1d506e49c0fd445b023a28e < b556c278d43f4707a9073ca74d55581b4f279806
Linux >= 4f1fffa2376922f3d1d506e49c0fd445b023a28e < 5c76f9961c170552c1d07c830b5e145475151600
Linux >= 6.6.32 < 6.6.117
Linux 6.8

Full technical detail▾

Overview

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_statfs+0x9f/0x2b0 [cifs f90b72658819bd21c94769b6a652029a07a7172f] statfs_by_dentry+0x67/0x90 vfs_statfs+0x16/0xd0 user_statfs+0x54/0xa0 __do_sys_statfs+0x20/0x50 do_syscall_64+0x58/0x80

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

References

Related vulnerabilities

Connected by shared product, vendor, weakness, or advisory.

#nvd#cve.org