Vulnerability in Linux kernel (CVE-2026-89540)
Summary
Vulnerability in Linux kernel (CVE-2026-89540). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
sunrpc: init gssp_lock before publishing proc entry
create_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy
via proc_create_data() before init_gssp_clnt() runs mutex_init() on
sn->gssp_lock. Once the dentry is linked under proc_subdir_lock it is
immediately reachable from userspace, so a write that lands in the
window drives set_gssp_clnt() into mutex_lock() on a zero-initialized
struct mutex.
create_use_gss_proxy_proc_entry(net)
proc_create_data("use-gss-proxy", ...) /* dentry live */
init_gssp_clnt(sn)
mutex_init(&sn->gssp_lock) /* too late */
write_gssp()
set_gssp_clnt(net)
mutex_lock(&sn->gssp_lock) /* uninitialized */
gssp_rpc_create(...)
sn->gssp_clnt = clnt
mutex_unlock(&sn->gssp_lock)
The window spans only the two statements between proc_create_data()
returning and init_gssp_clnt(), so a writer reaches it only if the
registering thread is preempted there while another task is already
opening the freshly published file. register_pernet_subsys() runs in
preemptible context under pernet_ops_rwsem, so that preemption is
possible, and the window widens on auth_rpcgss module load, when the
proc entry is created for every live net namespace whose tasks are
already running. A writer that wins the race locks a zero-filled
struct mutex. On CONFIG_DEBUG_MUTEXES the missing magic value trips a
"loc…
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-2026-89540 has been found in Linux kernel.
Successful exploitation can lead to full system takeover. CVSS score: 7.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-89540" on the vendor's site.
CVE-2026-89540 (Linux kernel) — CVSS v3 7.8
Attack vector: local / 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 7.8/10). Successful exploitation can lead to full system takeover.
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。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-89540 linux Fixed in: 6.1.190-1
- Ubuntu UBUNTU-CVE-2026-89540 linux
References
- advisory nvd.nist.gov
- advisory github.com
- package 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 git.kernel.org
- web github.com