CVE-2026-23364: Linux kernel · ksmbd: Compare MACs in constant time
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.4 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
- 0.4% chance of exploitation in 30 days – higher than 35% 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, 5.15.0-1118.128~20.04.1 +60
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 25 Mar 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 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle?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 has been fixed in updated kernel releases. Users should update their systems to the fixed versions to mitigate this vulnerability.
Description
A vulnerability in the Linux kernel's ksmbd component was resolved by changing the MAC comparison function to a constant-time implementation to prevent timing attacks. The issue involved using memcmp() for MAC comparisons, which is susceptible to timing attacks, and was fixed by replacing it with crypto_memneq(). This vulnerability affects multiple specific Linux kernel versions. A patch is available as part of the Linux kernel updates. The CVSS score is 7.4, indicating a medium severity level.
References
- ubuntu.com/security/CVE-2026-23364 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-23364 (opens in a new tab)
- git.kernel.org/linus/c5794709bc9105935dbedef8b9cf9c06f2b559fa (opens in a new tab)
- git.kernel.org/stable/c/2cdc56ed67615ba0921383a688f24415ebe065f3 (opens in a new tab)
- git.kernel.org/stable/c/307afccb751f542246bd5dc68a2c1ffe1a78418c (opens in a new tab)
- git.kernel.org/stable/c/93c0a22fec914ec4b697e464895a0f594e29fb28 (opens in a new tab)
- git.kernel.org/stable/c/c5794709bc9105935dbedef8b9cf9c06f2b559fa (opens in a new tab)
- git.kernel.org/stable/c/cd52a0e309659537048a864211abc3ea4c5caa63 (opens in a new tab)
- git.kernel.org/stable/c/f4588b85efd6007d46b80aa1b9fb746628ffb3dc (opens in a new tab)
- ubuntu.com/security/notices/USN-8567-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8596-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8606-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8607-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8608-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8609-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-3 (opens in a new tab)