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NVD / CVE Program· CNA Linux

CVE-2026-89706: nfsd: Reset write verifier when async COPY writeback fails

Noroxi assessment

Priority: Monitor (action score 30/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.52% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0, 5.10.270, 591134e059e3456180244a826d6917cdc183140b.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0, 5.10.270, 591134e059e3456180244a826d6917cdc183140b or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Sep 11, 2026
Updated
Oct 19, 2026
EPSS
0.5% · 44th percentile
CWE
—

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CNA vs NVD score

NVD
—
CNA · Linux
7.5
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.14affected
    • 817c6eb975798647c4bbbfc9eb288aa413ec7f65 and later · before cc5f7cef0659a27c13dd33edd8e2f79257b095c6affected · git
    • eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and later · before c6d2f6372c7e0f76b9c148ff7696aec64da0b5b7affected · git
    • eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and later · before 8a08ffe73eb2aa6bc6f88763da7e2b55bab6493aaffected · git
    • eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and later · before 6b13d26cc21b6320a3c61d5e4cee2ce9a589b181affected · git
    • eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and later · before 31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0affected · git
    • eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and later · before 591134e059e3456180244a826d6917cdc183140baffected · git
    • eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and later · before bf0cd31a9abcb728c17d79b4c2cc533612a8b6afaffected · git
    • eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and later · before f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9affected · git
    • 5.10.220 and later · before 5.10.270affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.190-16.1.190-1
Debian:12linux-6.12before 6.12.111-1~deb12u16.12.111-1~deb12u1
Debian:13linuxbefore 6.12.111-16.12.111-1
Debian:14linuxbefore 7.2.6-17.2.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-89704Sep 11, 2026 · nfsd: sample writeback error cursor before async COPY loop
    30Monitor
  • ← EarlierCVE-2026-89705Sep 11, 2026 · nfsd: restore rq_status_counter to even on all nfsd_dispatch() exit paths
    28Monitor
  • Later →CVE-2026-89707Sep 11, 2026 · nfsd: release path refs on follow_down() error
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0Vendor (CNA)
Linux Linux5.10.270Vendor (CNA)
Linux Linux591134e059e3456180244a826d6917cdc183140bVendor (CNA)
Linux Linux6b13d26cc21b6320a3c61d5e4cee2ce9a589b181Vendor (CNA)
Linux Linux8a08ffe73eb2aa6bc6f88763da7e2b55bab6493aVendor (CNA)
Linux Linuxbf0cd31a9abcb728c17d79b4c2cc533612a8b6afVendor (CNA)
Linux Linuxc6d2f6372c7e0f76b9c148ff7696aec64da0b5b7Vendor (CNA)
Linux Linuxcc5f7cef0659a27c13dd33edd8e2f79257b095c6Vendor (CNA)
Linux Linuxf5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9Vendor (CNA)
debian:linux6.1.190-1 · Debian:12Package registry (OSV)
debian:linux6.12.111-1 · Debian:13Package registry (OSV)
debian:linux-6.126.12.111-1~deb12u1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
None

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records