Vulnerability in Linux kernel (CVE-2026-89706)
Summary
Vulnerability in Linux kernel (CVE-2026-89706). Data can be tampered with by attackers.
Original description
The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-89706 has been found in Linux kernel.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-89706" on the vendor's site.
CVE-2026-89706 (Linux kernel) — CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (unclassified) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
References
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web nvd.nist.gov
- web github.com