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CVE-2026-89957 high CVSS 8.8

Vulnerability in Linux kernel (CVE-2026-89957)

Summary

Vulnerability in Linux kernel (CVE-2026-89957). 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:

s390/vfio-ap: Fix hot-unplug skipped when last AP adapter or domain removed

The vfio_ap_mdev_hot_unplug_cfg() function uses the return value of
bitmap_andnot() to determine whether the guest APCB needs to be updated.
However, bitmap_andnot() returns false when the resulting destination
bitmap is empty. This means that if the only adapter, domain or control
domain assigned to an mdev is removed from the host's AP configuration,
the bit is correctly cleared from the shadow APCB, but bitmap_andnot()
returns false because the result is an empty bitmap. Consequently,
do_hotplug remains 0 and vfio_ap_mdev_update_guest_apcb() is never called,
leaving the KVM guest with stale hardware access to the unplugged AP
devices.

Fix this by replacing the bitmap_andnot() return value check with
bitmap_intersects() to determine whether the shadow APCB actually
overlaps with the removal mask. If there is an intersection, call
bitmap_andnot() solely for its side effect of clearing the bits, then
unconditionally set do_hotplug to trigger the guest APCB update.

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-2026-89957 has been found in Linux kernel.
Successful exploitation can lead to full system takeover. CVSS score: 8.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-89957" on the vendor's site.

CVE-2026-89957 (Linux kernel) — CVSS v3 8.8
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.

❓ What is the problem

A vulnerability (unclassified) exists in Linux kernel.

📍 Affected scope

Check the vendor advisory for the affected versions of Linux kernel.

🔥 Severity

Severity: High (CVSS 8.8/10). Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

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

  1. 1
    Identify 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。

  2. 2
    Post-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

References

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