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High 7.8

Vulnerability in Linux kernel

CVE-2025-21823 First seen on SecPulse

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-2025-21823 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-2025-21823" on the vendor's site.

CVE-2025-21823 (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.

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 7.8/10). 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 exposureidentify
    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 verificationverify
    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

EcosystemPackageAffectedFixed
Linux Kernel
≥ 4.6.0, < 5.4.291
≥ 5.5.0, < 5.10.235
≥ 5.11.0, < 5.15.179
≥ 5.16.0, < 6.1.129
≥ 6.2.0, < 6.6.79
≥ 6.7.0, < 6.12.16
+1 more
5.4.291
5.10.235
5.15.179
6.1.129
6.6.79
6.12.16

Fix status by distribution

Fixed packages published by each distribution for this CVE

Original description The description as published by the source.

In the Linux kernel, the following vulnerability has been resolved:

batman-adv: Drop unmanaged ELP metric worker

The ELP worker needs to calculate new metric values for all neighbors
"reachable" over an interface. Some of the used metric sources require
locks which might need to sleep. This sleep is incompatible with the RCU
list iterator used for the recorded neighbors. The initial approach to work
around of this problem was to queue another work item per neighbor and then
run this in a new context.

Even when this solved the RCU vs might_sleep() conflict, it has a major
problems: Nothing was stopping the work item in case it is not needed
anymore - for example because one of the related interfaces was removed or
the batman-adv module was unloaded - resulting in potential invalid memory
accesses.

Directly canceling the metric worker also has various problems:

  • cancel_work_sync for a to-be-deactivated interface is called with
    rtnl_lock held. But the code in the ELP metric worker also tries to use
    rtnl_lock() - which will never return in this case. This also means that
    cancel_work_sync would never return because it is waiting for the worker
    to finish.
  • iterating over the neighbor list for the to-be-deactivated interface is
    currently done using the RCU specific methods. Which means that it is
    possible to miss items when iterating over it without the associated
    spinlock - a behaviour which is acceptable for a periodic metric check
    but not for a cleanup rout…

Source: NIST National Vulnerability Database NVD

References

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