CVE-2025-38527
Linux Kernel use-after-free
- Published16 Aug 2025
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 3.1 breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HAffected products
Remediation
- https://git.kernel.org/stable/c/09bce2138a30ef10d8821c8c3f73a4ab7a5726bc
- https://git.kernel.org/stable/c/0a4eec84d4d2c4085d4ed8630fd74e4b39033c1b
- https://git.kernel.org/stable/c/2baaf5bbab2ac474c4f92c10fcb3310f824db995
- https://git.kernel.org/stable/c/4256a483fe58af66a46cbf3dc48ff26e580d3308
- https://git.kernel.org/stable/c/705c79101ccf9edea5a00d761491a03ced314210
- https://git.kernel.org/stable/c/da11bd4b697b393a207f19a2ed7d382a811a3ddc
References
- https://git.kernel.org/stable/c/09bce2138a30ef10d8821c8c3f73a4ab7a5726bc
- https://git.kernel.org/stable/c/0a4eec84d4d2c4085d4ed8630fd74e4b39033c1b
- https://git.kernel.org/stable/c/2baaf5bbab2ac474c4f92c10fcb3310f824db995
- https://git.kernel.org/stable/c/4256a483fe58af66a46cbf3dc48ff26e580d3308
- https://git.kernel.org/stable/c/705c79101ccf9edea5a00d761491a03ced314210
- https://git.kernel.org/stable/c/da11bd4b697b393a207f19a2ed7d382a811a3ddc
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
Related CVEs
Recent high-severity vulnerabilities sharing a weakness type.
Frequently asked
Is CVE-2025-38527 being actively exploited?
CVE-2025-38527 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.41%.
How severe is CVE-2025-38527?
CVE-2025-38527 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.41% probability of exploitation.
Which products are affected by CVE-2025-38527?
Affected products include Debian Linux, Linux Kernel.
How do I fix CVE-2025-38527?
Upgrade affected software to a fixed version, for example Linux Kernel 3.17 or later, then confirm no affected versions remain in your inventory.
How Secuno handles this
Secuno correlates vulnerabilities like CVE-2025-38527 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.
Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.