CVE-2025-38527

High

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix use-after-free in cifs_oplock_break A race condition can occur in cifs_oplock_break() leading to a use-after-free of the cinode structure when unmounting: cifs_oplock_break() _cifsFileInfo_put(cfile) cifsFileInfo_put_final() cifs_sb_deactive() [last ref, start releasing sb] kill_sb() kill_anon_super() generic_shutdown_super() evict_inodes() dispose_list() evict() destroy_inode() call_rcu(&inode->i_rcu, i_callback) spin_lock(&cinode->open_file_lock) <- OK [later] i_callback() cifs_free_inode() kmem_cache_free(cinode) spin_unlock(&cinode->open_file_lock) <- UAF cifs_done_oplock_break(cinode) <- UAF The issue occurs when umount has already released its reference to the superblock. When _cifsFileInfo_put() calls cifs_sb_deactive(), this releases the last reference, triggering the immediate cleanup of all inodes under RCU. However, cifs_oplock_break() continues to access the cinode after this point, resulting in use-after-free. Fix this by holding an extra reference to the superblock during the entire oplock break operation. This ensures that the superblock and its inodes remain valid until the oplock break completes.

Package Linux Kernel
Published 2025-08-16
Last modified 2026-01-07
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

7.8

out of 10
High
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-416

CVE-2025-38527 is a Use After Free vulnerability

What is Use After Free?

The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. Learn more on MITRE CWE

Affected versions

Linux kernel versions 3.16.72, 4.9.171, 4.14.114, 4.19.37, 5.0.10, 5.1 and later are affected. Fixed in 5.15.190, 6.1.147, 6.6.100, 6.12.40, 6.15.8, 6.16 and their respective stable series.

Affected from
≥ 3.16.72 ≥ 4.9.171 ≥ 4.14.114 ≥ 4.19.37 ≥ 5.0.10 ≥ 5.1
Fixed in
✓ 5.15.190 5.15.x ✓ 6.1.147 6.1.x ✓ 6.6.100 6.6.x ✓ 6.12.40 6.12.x ✓ 6.15.8 6.15.x ✓ 6.16

References

The following references provide additional information about CVE-2025-38527 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

6 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2025-38527?

    CVE-2025-38527 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 , classified as an Use After Free flaw (CWE-416) . It affects Linux kernel versions from 3.16.72 onward and has been patched in 5.15.190, 6.1.147, 6.6.100 and others. CVE-2025-38527 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2025-38527?

    CVE-2025-38527 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H .

  • Is there a patch available for CVE-2025-38527?

    Yes — CVE-2025-38527 has been patched. Fixed versions include 5.15.190, 6.1.147, 6.6.100 and others. If you are running Linux kernel 3.16.72 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2025-38527 actively exploited?

    No — CVE-2025-38527 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is Use After Free (CWE-416)?

    The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. View CWE-416 on MITRE CWE →

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