CVE-2025-38527
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-08-16

Last updated on: 2025-11-03

Assigner: kernel.org

Description
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.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2025-08-16
Last Modified
2025-11-03
Generated
2026-05-27
AI Q&A
2025-08-16
EPSS Evaluated
2026-05-25
NVD
CVE-2025-38527
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 6.1.153-1
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a use-after-free issue in the Linux kernel's SMB client code, specifically in the cifs_oplock_break() function. A race condition can occur during the unmounting process where the cinode structure is accessed after it has been freed. This happens because the last reference to the superblock is released prematurely, triggering cleanup of inodes, but cifs_oplock_break() continues to use the freed cinode. The fix involves holding an extra reference to the superblock during the oplock break operation to prevent premature freeing.


How can this vulnerability impact me? :

This vulnerability can lead to use-after-free memory corruption in the Linux kernel when using SMB client functionality. Exploiting this could cause system instability, crashes, or potentially allow an attacker to execute arbitrary code with kernel privileges, compromising system security.


What immediate steps should I take to mitigate this vulnerability?

To mitigate this vulnerability, update the Linux kernel to a version where the use-after-free issue in cifs_oplock_break() has been fixed. The fix involves holding an extra reference to the superblock during the oplock break operation to prevent premature cleanup. Until the update is applied, avoid unmounting CIFS shares in a way that triggers this race condition.


Ask Our AI Assistant
Need more information? Ask your question to get an AI reply (Powered by our expertise)
0/70
EPSS Chart