CVE-2026-89706nfsd: Reset write verifier when async COPY writeback fails
- 7.5HighCVSS base score
- 0.53%Exploitation in 30 daysEPSS · top 55% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: Reset write verifier when async COPY writeback fails Async COPY captures nn->writeverf at request time and reports it to the client via CB_OFFLOAD after the worker kthread completes. When the post-copy vfs_fsync_range() or filemap_check_wb_err() in _nfsd_copy_file_range() reports an error, the worker correctly leaves NFSD4_COPY_F_COMMITTED clear so that CB_OFFLOAD encodes wr_stable_how as NFS_UNSTABLE, but the server's write verifier is not rotated. A client that receives NFS_UNSTABLE in CB_OFFLOAD follows up with COMMIT to make the copied data durable. With the verifier unchanged, COMMIT returns the same value the client just received via CB_OFFLOAD, and the client concludes the copy is durable -- silently dropping the data whose writeback in fact failed. This violates the UNSTABLE+COMMIT durability contract (RFC 7862 section 15.1, RFC 8881 section 18.32) and matches the bug just fixed in nfsd_vfs_write() and nfsd_commit(). Rotate nn->writeverf at the writeback-failure site. The async COPY worker has no svc_rqst, so commit_reset_write_verifier() is not available here; calling nfsd_reset_write_verifier() directly mirrors the trace-less reset already used by nfsd_file_check_write_error() for the same purpose. Filter out -EAGAIN and -ESTALE, matching commit_reset_write_verifier(), since neither indicates a durable-storage failure.
Timeline
ID reserved
By Linux
Published
- 38 days later
· 38 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
| NVDNVD · Received | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.53% · top 55% of all CVEs (14 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Affected products
- affected 817c6eb975798647c4bbbfc9eb288aa413ec7f65 – < cc5f7cef0659a27c13dd33edd8e2f79257b095c6
- affected eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d – < c6d2f6372c7e0f76b9c148ff7696aec64da0b5b7
- affected eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d – < 8a08ffe73eb2aa6bc6f88763da7e2b55bab6493a
- affected eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d – < 6b13d26cc21b6320a3c61d5e4cee2ce9a589b181
- affected eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d – < 31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0
- affected eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d – < 591134e059e3456180244a826d6917cdc183140b
- affected eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d – < bf0cd31a9abcb728c17d79b4c2cc533612a8b6af
- affected eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d – < f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9
- affected 5.10.220 – < 5.10.270
- affected 5.14
- unaffected < 5.14
- unaffected 5.10.270 – ≤ 5.10.*
- unaffected 5.15.221 – ≤ 5.15.*
- unaffected 6.1.188 – ≤ 6.1.*
- unaffected 6.6.157 – ≤ 6.6.*
- unaffected 6.12.109 – ≤ 6.12.*
- unaffected 6.18.50 – ≤ 6.18.*
- unaffected 7.2.4 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References8
- https://git.kernel.org/stable/c/cc5f7cef0659a27c13dd33edd8e2f79257b095c6 (opens in a new tab)
- https://git.kernel.org/stable/c/c6d2f6372c7e0f76b9c148ff7696aec64da0b5b7 (opens in a new tab)
- https://git.kernel.org/stable/c/8a08ffe73eb2aa6bc6f88763da7e2b55bab6493a (opens in a new tab)
- https://git.kernel.org/stable/c/6b13d26cc21b6320a3c61d5e4cee2ce9a589b181 (opens in a new tab)
- https://git.kernel.org/stable/c/31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0 (opens in a new tab)
- https://git.kernel.org/stable/c/591134e059e3456180244a826d6917cdc183140b (opens in a new tab)
- https://git.kernel.org/stable/c/bf0cd31a9abcb728c17d79b4c2cc533612a8b6af (opens in a new tab)
- https://git.kernel.org/stable/c/f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-76618 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://cveledger.app/cve/CVE-2026-89706)Record last updated .