CVE-2025-40103: Linux kernel · smb: client: Fix refcount leak for cifs_sb_tlink
Affects Linux kernelSource GCVE Database
Not known to be exploited · fixed in 6.8.0-1050.53~22.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 10:12 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.8.0-1050.53~22.04.1, 6.8.0-1051.57~22.04.1, 6.8.0-1052.55~22.04.1 +35
Exploitation evidence
Disclosed: evidence found.
CVE published 30 Oct 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.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linuxpkg:deb/ubuntu/linux@6.17.0-14.14?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws@6.17.0-1007.7?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure@6.17.0-1008.8?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp@6.17.0-1007.7?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle@6.17.0-1007.7?arch=source&distro=questingOther 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 should be applied to affected Linux kernel versions. The vendor advisory from Ubuntu confirms that this issue is fixed in updated kernel releases. Users should update their Linux kernel to versions beyond the affected ones to remediate this vulnerability.
Description
A refcount leak vulnerability in the Linux kernel's SMB client implementation related to the cifs_sb_tlink structure has been resolved. The issue involved three refcount inconsistency problems where calls to cifs_sb_tlink did not properly update reference counts, potentially causing resource leaks. This flaw was fixed in Linux kernel updates addressing multiple security issues across various subsystems. The vulnerability affects specific Linux kernel versions and has a medium severity rating.
References
- ubuntu.com/security/CVE-2025-40103 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-40103 (opens in a new tab)
- git.kernel.org/linus/c2b77f42205ef485a647f62082c442c1cd69d3fc (opens in a new tab)
- git.kernel.org/stable/c/790282abe9d805f08618c1c24ea2529e7259b692 (opens in a new tab)
- git.kernel.org/stable/c/896bb31e1416f582503db1350cf1bd10dc64e5a6 (opens in a new tab)
- git.kernel.org/stable/c/c2b77f42205ef485a647f62082c442c1cd69d3fc (opens in a new tab)
- git.kernel.org/stable/c/d7dd034c14928306db1b46be277ae439b84dacf9 (opens in a new tab)
- git.kernel.org/stable/c/e15605b68b490186da2ad8029c0351a9cfb0b9af (opens in a new tab)
- ubuntu.com/security/notices/USN-8029-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8030-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8029-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8048-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8029-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8100-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8125-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8126-1 (opens in a new tab)