CVE-2025-38527: Linux kernel · smb: client: fix use-after-free in cifs_oplock_break
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical · fixed in 5.15.0-1097.104~20.04.1 : patch Linux kernel as a priority.
Data as of 28 Oct 2026, 11:27 UTC
- Patch
- Available – fixed in 5.15.0-1097.104~20.04.1, 5.15.0-1102.111~20.04.1, 5.15.0-1097.106~20.04.1 +63
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 16 Aug 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-7879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7880-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7933-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-aws-6.14pkg:deb/ubuntu/linux-aws-6.14?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A patch is available and has been released in multiple fixed Linux kernel versions including 5.15.0-1097.104~20.04.1 and later. Users and administrators should apply these kernel updates promptly to remediate the vulnerability. No additional mitigation steps are indicated beyond applying the official fixes provided by the vendor.
Description
A critical use-after-free vulnerability (CVE-2025-38527) exists in the Linux kernel's SMB client implementation in the cifs_oplock_break function. This flaw arises from a race condition during unmounting, where the cinode structure is accessed after it has been freed, potentially leading to system compromise. The issue is fixed by holding an extra reference to the superblock during the oplock break operation to prevent premature cleanup. Multiple Linux kernel versions prior to 5.15.0-1097.104~20.04.1 and specific 4.11 and 4.13 versions are affected. A patch is available and should be applied to mitigate the vulnerability.
References
- ubuntu.com/security/CVE-2025-38527 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-38527 (opens in a new tab)
- git.kernel.org/linus/705c79101ccf9edea5a00d761491a03ced314210 (opens in a new tab)
- git.kernel.org/stable/c/09bce2138a30ef10d8821c8c3f73a4ab7a5726bc (opens in a new tab)
- git.kernel.org/stable/c/0a4eec84d4d2c4085d4ed8630fd74e4b39033c1b (opens in a new tab)
- git.kernel.org/stable/c/2baaf5bbab2ac474c4f92c10fcb3310f824db995 (opens in a new tab)
- git.kernel.org/stable/c/705c79101ccf9edea5a00d761491a03ced314210 (opens in a new tab)
- git.kernel.org/stable/c/da11bd4b697b393a207f19a2ed7d382a811a3ddc (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7880-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7879-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7933-1 (opens in a new tab)