CVE-2026-43350: Linux kernel · smb: client: require a full NFS mode SID before reading mode bits
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.6 High · fixed in 5.15.0-1117.124~20.04.1 : patch Linux kernel soon.
Data as of 26 Oct 2026, 12:55 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 25% 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 +69
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:HExploitation evidence
Disclosed: evidence found.
CVE published 8 May 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-ibmpkg:deb/ubuntu/linux-ibm?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 confirms that this and other Linux kernel vulnerabilities have been fixed. Users should update their Linux kernel packages to the fixed versions as provided by their distribution. No additional mitigation steps are required beyond applying the official fix.
Description
A vulnerability in the Linux kernel SMB client was resolved that involved improper handling of NFS mode SIDs in the parse_dacl() function. The flaw allowed a malicious server to craft an Access Control Entry (ACE) with fewer subauthorities than expected, causing the kernel to read memory beyond the ACE boundary. This could lead to information disclosure or system instability. The issue was fixed by requiring the ACE to have at least three subauthorities before processing it as an NFS mode SID.
References
- ubuntu.com/security/CVE-2026-43350 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-43350 (opens in a new tab)
- git.kernel.org/linus/2757ad3e4b6f9e0fed4c7739594e702abc5cab21 (opens in a new tab)
- git.kernel.org/stable/c/2757ad3e4b6f9e0fed4c7739594e702abc5cab21 (opens in a new tab)
- git.kernel.org/stable/c/38a69f08ee82c450d3e4168707fff2e317dc3ff7 (opens in a new tab)
- git.kernel.org/stable/c/b53b8e98c23310294fc45fc686db5ee860311896 (opens in a new tab)
- git.kernel.org/stable/c/c8eef12af1cc73031639ea7cf16e0b10e2536b0b (opens in a new tab)
- git.kernel.org/stable/c/f8488c07bea2431ee12a6067d736578064fa46b4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8488-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8488-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8507-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8569-1 (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-8603-1 (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)