Vulnerability in Linux kernel (CVE-2026-89664)
Summary
Vulnerability in Linux kernel (CVE-2026-89664). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
nfsd: release OPEN-decoded posix ACLs via op_release
nfsd4_decode_createhow4() calls nfsd4_decode_fattr4(), which allocates
refcounted struct posix_acl objects via posix_acl_alloc() and stores
them in open->op_pacl and open->op_dpacl. These pointers must be
released once the OPEN compound finishes.
When nfsd4_decode_open_claim4() returns a non-seqid-mutating error,
the dispatcher short-circuits before op_func runs:
nfsd4_proc_compound()
if (op->status && op->opnum == OP_OPEN)
op->status = nfsd4_open_omfg(...)
if (!seqid_mutating_err(ntohl(op->status)))
return op->status; /* nfsd4_open() never runs */
...
opdesc->op_release(&op->u) /* must still release op_pacl/op_dpacl */
Before this change OP_OPEN had no .op_release in nfsd4_ops[], and the
release pair lived inside nfsd4_open() at its out_err: label. On the
short-circuit path nfsd4_open() is never invoked, so both posix_acl
refs leak on every malformed OPEN compound that carries valid POSIX
ACL createhow4 attributes.
Add nfsd4_open_release() and wire it as .op_release for OP_OPEN.
posix_acl_release() is NULL-safe, so the single release site covers
both the normal path and the nfsd4_open_omfg short-circuit. Remove
the matching posix_acl_release() pair from nfsd4_open()'s out_err:
label to avoid double-releasing.
The compound loop has two encoding branches: nfsd4_encode_operation()
for n…
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-2026-89664 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure. 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-2026-89664" on the vendor's site.
CVE-2026-89664 (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). Risk of unauthorized operations or information disclosure.
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。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-89664 linux-hwe-edge
References
- web git.kernel.org
- web git.kernel.org
- web nvd.nist.gov
- web github.com