CVE-2026-89711: Linux kernel · NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 8.2 High.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 38% 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:L/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 is available that removes the flawed WARN_ON_ONCE and retains the necessary error return to prevent NULL pointer dereference. Users should apply the updated Linux kernel versions that include this fix. Since this is a kernel-level vulnerability, updating to patched kernel versions is the recommended remediation.
Description
A vulnerability in the Linux kernel's NFSD component related to an incorrect WARN_ON_ONCE usage in nfsd_mode_check() has been resolved. The flawed assumption that justified the WARN_ON_ONCE was invalid in cases of NFS reexport, potentially leading to a NULL pointer dereference. The fix removes the WARN_ON_ONCE while retaining the nfserr_notdir return to prevent dereferencing a NULL method pointer during client LOOKUP operations.
References
- nvd.nist.gov/vuln/detail/CVE-2026-89711 (opens in a new tab)
- git.kernel.org/stable/c/7ef182a8fe9c12b0d936880b1e504840639aa009 (opens in a new tab)
- git.kernel.org/stable/c/a275de3bac5635514ca830f2e46b5ff0e66b5c4c (opens in a new tab)
- git.kernel.org/stable/c/aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e (opens in a new tab)
- git.kernel.org/stable/c/b55b4d880bb080fa10eb08ba21a5d8679b8102fe (opens in a new tab)
- ubuntu.com/security/CVE-2026-89711 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89711 (opens in a new tab)
- git.kernel.org/linus/aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e (opens in a new tab)