CVE-2025-38191: Linux kernel · ksmbd: fix null pointer dereference in destroy_previous_session
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.5 High · fixed in 6.8.0-1046.49~22.04.1 : patch Linux kernel soon.
Data as of 26 Oct 2026, 12:55 UTC
- EPSS
- 1.4% chance of exploitation in 30 days – higher than 72% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.8.0-1046.49~22.04.1, 6.8.0-1051.57~22.04.1, 6.8.0-1047.50~22.04.2 +30
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 4 Jul 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 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux@6.8.0-100.100?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws@6.8.0-1046.49?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-aws-6.14pkg:deb/ubuntu/linux-aws-6.14@6.14.0-1015.15~24.04.1?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure@6.8.0-1046.52?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11@6.11.0-1018.18~24.04.1?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 should be applied to affected Linux kernel versions. The vendor advisory confirms the issue is fixed. Users should update to patched kernel versions to remediate this vulnerability.
Description
A null pointer dereference vulnerability in the Linux kernel's ksmbd component was fixed. The issue occurs during Kerberos session setup if the client sets the PreviousSessionId, leading to a NULL pointer dereference because sess->user is not yet set when destroy_previous_session() is called. The patch moves the call to destroy_previous_session() after ksmbd_krb5_authenticate() to ensure sess->user is properly initialized. This vulnerability can cause a denial of service due to kernel crash. Multiple specific Linux kernel versions are affected.
References
- ubuntu.com/security/CVE-2025-38191 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-38191 (opens in a new tab)
- git.kernel.org/linus/7ac5b66acafcc9292fb935d7e03790f2b8b2dc0e (opens in a new tab)
- git.kernel.org/stable/c/076f1adefb9837977af7ed233883842ddc446644 (opens in a new tab)
- git.kernel.org/stable/c/0902625a24eea7fdc187faa5d97df244d159dd6e (opens in a new tab)
- git.kernel.org/stable/c/1193486dffb7432a09f57f5d09049b4d4123538b (opens in a new tab)
- git.kernel.org/stable/c/281afc52e2961cd5dd8326ebc9c5bc40904c0468 (opens in a new tab)
- git.kernel.org/stable/c/7ac5b66acafcc9292fb935d7e03790f2b8b2dc0e (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7834-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7833-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7856-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8031-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-5 (opens in a new tab)