Linux azure: 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… (CVE-2025-38527)
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.
AI Analysis
Technical Summary
This advisory covers two security fixes in the Red Hat kernel-rt packages. The first fix addresses a use-after-free vulnerability in the SMB client code within the cifs_oplock_break function (CVE-2025-38527). The second fix corrects improper filehandle bounds checking in the nfs_fh_to_dentry() function (CVE-2025-39730). Both issues could potentially lead to memory corruption or other stability problems. Red Hat has released updated kernel-rt packages for Red Hat Enterprise Linux 8 Real Time variants to remediate these vulnerabilities. The update is rated as having moderate security impact. No CVSS scores are provided in the advisory, but Red Hat’s classification and the nature of the fixes indicate a medium severity level.
Potential Impact
The vulnerabilities fixed involve memory safety issues: a use-after-free in SMB client code and improper bounds checking in NFS filehandle processing. Such flaws can lead to memory corruption, which may cause system instability or potentially allow an attacker to execute arbitrary code or cause denial of service. However, Red Hat rates the overall impact as moderate, indicating that exploitation may require specific conditions or have limited scope.
Mitigation Recommendations
Red Hat has released updated kernel-rt packages that address these vulnerabilities. Users of affected Red Hat Enterprise Linux for Real Time 8 variants should apply the security update as detailed in the Red Hat advisory RHSA-2025:17398 and reboot their systems to ensure the fixes take effect. No additional mitigation steps are indicated or required beyond applying the official update and rebooting.
Linux azure: 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… (CVE-2025-38527)
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 v3.1
Score 9.8critical
Affected software
pkg:rpm/redhat/kernel-rtRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This advisory covers two security fixes in the Red Hat kernel-rt packages. The first fix addresses a use-after-free vulnerability in the SMB client code within the cifs_oplock_break function (CVE-2025-38527). The second fix corrects improper filehandle bounds checking in the nfs_fh_to_dentry() function (CVE-2025-39730). Both issues could potentially lead to memory corruption or other stability problems. Red Hat has released updated kernel-rt packages for Red Hat Enterprise Linux 8 Real Time variants to remediate these vulnerabilities. The update is rated as having moderate security impact. No CVSS scores are provided in the advisory, but Red Hat’s classification and the nature of the fixes indicate a medium severity level.
Potential Impact
The vulnerabilities fixed involve memory safety issues: a use-after-free in SMB client code and improper bounds checking in NFS filehandle processing. Such flaws can lead to memory corruption, which may cause system instability or potentially allow an attacker to execute arbitrary code or cause denial of service. However, Red Hat rates the overall impact as moderate, indicating that exploitation may require specific conditions or have limited scope.
Mitigation Recommendations
Red Hat has released updated kernel-rt packages that address these vulnerabilities. Users of affected Red Hat Enterprise Linux for Real Time 8 variants should apply the security update as detailed in the Red Hat advisory RHSA-2025:17398 and reboot their systems to ensure the fixes take effect. No additional mitigation steps are indicated or required beyond applying the official update and rebooting.
Technical Details
- Gcve Source
- db.gcve.eu
- Csaf Category
- csaf_security_advisory
- Csaf Version
- 2.0
- Publisher
- Red Hat Product Security
- Advisory Id
- RHSA-2025:17398
- Cve Count
- 2
- Additional Cves
- ["CVE-2025-39730"]
Threat ID: 6a3da1e24853345fc182c396
Added to database: 06/25/2026, 21:47:14 UTC
Last enriched: 06/25/2026, 22:28:57 UTC
Last updated: 09/10/2026, 19:36:50 UTC
Views: 55
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