CVE-2026-89664: Linux kernel · nfsd: release OPEN-decoded posix ACLs via op_release
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.5 High.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 41% 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:N/I:N/A:HExploitation 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 for this vulnerability has been implemented in the Linux kernel. Users should apply the official kernel updates that include the patch for CVE-2026-89664 to ensure proper resource release in nfsd. Since this is a kernel-level issue, upgrading to a patched kernel version is the recommended remediation. Patch status is not explicitly stated in the input, so users should consult their Linux distribution's security advisories for the availability of updates.
Description
A vulnerability in the Linux kernel's NFS server (nfsd) was resolved that caused a resource leak of POSIX ACL objects during malformed OPEN compound operations. The issue arises when certain error conditions short-circuit normal processing, preventing proper release of allocated ACL references. This can lead to resource exhaustion on affected systems. The flaw affects specific Linux kernel versions used in the linux-hwe-edge product line. The vulnerability has a CVSS score of 7.5 and is classified as medium severity.
References
- nvd.nist.gov/vuln/detail/CVE-2026-89664 (opens in a new tab)
- git.kernel.org/stable/c/5b3a7d7c23c071efe12dd1bc1d2e5f97c4892921 (opens in a new tab)
- git.kernel.org/stable/c/8215892993ea9f5231da4fa9eb42428a286fce8b (opens in a new tab)
- ubuntu.com/security/CVE-2026-89664 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89664 (opens in a new tab)
- git.kernel.org/linus/8215892993ea9f5231da4fa9eb42428a286fce8b (opens in a new tab)