CVE-2026-74521: Linux kernel · ksmbd: use memcmp() to compare ClientGUIDs
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.1 Critical : upgrade to 6.8.0-1035.38 as a priority.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.8.0-1035.38
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 15 Aug 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 the Ubuntu linux-nvidia-tegra package to 6.8.0-1035.38.
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.
Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: use memcmp() to compare ClientGUIDs ClientGUID is a fixed-size binary value and can contain embedded NUL bytes. strncmp() stops comparing at the first NUL byte, so different ClientGUID values can incorrectly be treated as equal. Use memcmp() in SMB3 multichannel session binding and FSCTL_VALIDATE_NEGOTIATE_INFO to compare all SMB2_CLIENT_GUID_SIZE bytes.
References
- ubuntu.com/security/CVE-2026-74521 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-74521 (opens in a new tab)
- git.kernel.org/linus/e8bb506e6ef749ac0336f3e579d8d02396b7d832 (opens in a new tab)
- git.kernel.org/stable/c/d535363299822c5caa543787b21bd5cfa3e41949 (opens in a new tab)
- git.kernel.org/stable/c/e8bb506e6ef749ac0336f3e579d8d02396b7d832 (opens in a new tab)
- ubuntu.com/security/notices/USN-8781-1 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-74521 (opens in a new tab)
- git.kernel.org/stable/c/5a0367bf5ce420be7b19936def2e90adcf32a683 (opens in a new tab)
- git.kernel.org/stable/c/7bde6f181fa307d2cc1ec2b0313ac8e9811c8232 (opens in a new tab)
- git.kernel.org/stable/c/a386c83043015a703e227775f778e40343f45911 (opens in a new tab)
- git.kernel.org/stable/c/ba2a5b66f1d414eb8403d655f8813783892cfc85 (opens in a new tab)