CVE-2026-89706: Linux kernel · nfsd: Reset write verifier when async COPY writeback fails
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.5 High.
Data as of 26 Oct 2026, 12:55 UTC
- EPSS
- 0.5% chance of exploitation in 30 days – higher than 44% 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: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 rotates the write verifier correctly on async COPY writeback failures. Users should apply the updated Linux kernel versions that include this fix to ensure proper writeback failure handling and maintain NFS data integrity.
Description
A vulnerability in the Linux kernel's NFS server (nfsd) was fixed involving improper handling of write verifiers during asynchronous COPY writeback failures. When the async COPY writeback fails, the server did not rotate the write verifier, causing clients to mistakenly believe that data was durably written when it was not, violating the NFS protocol's durability guarantees.
References
- nvd.nist.gov/vuln/detail/CVE-2026-89706 (opens in a new tab)
- git.kernel.org/stable/c/31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0 (opens in a new tab)
- git.kernel.org/stable/c/591134e059e3456180244a826d6917cdc183140b (opens in a new tab)
- git.kernel.org/stable/c/bf0cd31a9abcb728c17d79b4c2cc533612a8b6af (opens in a new tab)
- git.kernel.org/stable/c/f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9 (opens in a new tab)
- ubuntu.com/security/CVE-2026-89706 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89706 (opens in a new tab)
- git.kernel.org/linus/f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9 (opens in a new tab)