CVE-2026-89671: Linux kernel · nfsd: gate nfs3 setacl by argp->mask
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.1 Critical.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.5% chance of exploitation in 30 days – higher than 42% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
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 11 Sep 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
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 fix is available that properly checks the mask bits before calling set_posix_acl() in the nfsd3_proc_setacl() function, preventing unintended ACL removals. Users should apply the updated Linux kernel versions that include this patch. Since this is a kernel vulnerability, updating to a patched kernel version is the recommended remediation. No additional mitigation steps are indicated.
Description
A vulnerability in the Linux kernel's NFSv3 server implementation allows improper handling of Access Control Lists (ACLs) during the SETACL operation. The function nfsd3_proc_setacl() calls set_posix_acl() unconditionally for both ACL_TYPE_ACCESS and ACL_TYPE_DEFAULT, passing pointers that may be NULL. This causes the server to confuse a missing ACL pointer with a request to remove that ACL, leading to unintended ACL removals when certain mask bits are not set. The issue has been fixed by adding checks on the mask bits before calling set_posix_acl(), preventing accidental ACL deletions.
References
- nvd.nist.gov/vuln/detail/CVE-2026-89671 (opens in a new tab)
- git.kernel.org/stable/c/453d7198a0ab07a12d46e0575861ac7b932da17e (opens in a new tab)
- git.kernel.org/stable/c/68a80b26efdff1d09f8ae1773c6a915abb9e191d (opens in a new tab)
- git.kernel.org/stable/c/b3bff820d068ea59767d4e91a3258231a879da5f (opens in a new tab)
- git.kernel.org/stable/c/ff99ed007f065198fd723152405c22aa558f700b (opens in a new tab)
- ubuntu.com/security/CVE-2026-89671 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89671 (opens in a new tab)
- git.kernel.org/linus/453d7198a0ab07a12d46e0575861ac7b932da17e (opens in a new tab)