CVE-2026-64401: Linux kernel · smb: client: resolve SWN tcon from live registrations
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 5.15.0-1117.124~20.04.1 : patch Linux kernel soon.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +44
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 25 Jul 2026
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 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther 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 (USN-8726-1) confirms that this issue has been fixed in updated kernel packages. Users should update to the fixed kernel versions as soon as possible to mitigate this vulnerability.
Description
A use-after-free vulnerability in the Linux kernel's SMB client subsystem (CVE-2026-64401) was resolved. The issue involved improper handling of cached tcon pointers in witness registrations, leading to potential use of freed memory and violation of CIFS lock order. The fix ensures that only stable witness identity information is stored and live tcon references are pinned during notification handling, preventing use-after-free conditions. This vulnerability affects multiple Linux kernel versions prior to 7.0.0-31.31 and specific other versions listed. A patch is available to address this flaw.
References
- nvd.nist.gov/vuln/detail/CVE-2026-64401 (opens in a new tab)
- git.kernel.org/stable/c/0700f946659d0ab2352ec8a9b1c6fc74b13a27d7 (opens in a new tab)
- git.kernel.org/stable/c/51d18db392e5386a7bb9e816d611f14e600cca3c (opens in a new tab)
- git.kernel.org/stable/c/91b8a58c6ac15c7db6518f696389933282f88da7 (opens in a new tab)
- git.kernel.org/stable/c/945b4a4a54497db1dcb2f20ef801a84e884dac21 (opens in a new tab)
- git.kernel.org/stable/c/aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd (opens in a new tab)
- git.kernel.org/stable/c/ec457f9afe5ae9538bdcd58fd4cb442b9787e183 (opens in a new tab)
- ubuntu.com/security/CVE-2026-64401 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-64401 (opens in a new tab)
- git.kernel.org/linus/ec457f9afe5ae9538bdcd58fd4cb442b9787e183 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8727-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8760-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8800-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8760-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-3 (opens in a new tab)