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High 7.8

Vulnerability in Linux kernel

CVE-2025-21664 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-2025-21664 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-2025-21664" on the vendor's site.

CVE-2025-21664 (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
≥ 3.15.0, < 5.4.290
≥ 5.5.0, < 5.10.234
≥ 5.11.0, < 5.15.177
≥ 5.16.0, < 6.1.125
≥ 6.2.0, < 6.6.72
≥ 6.7.0, < 6.12.10
5.4.290
5.10.234
5.15.177
6.1.125
6.6.72
6.12.10

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:

dm thin: make get_first_thin use rcu-safe list first function

The documentation in rculist.h explains the absence of list_empty_rcu()
and cautions programmers against relying on a list_empty() ->
list_first() sequence in RCU safe code. This is because each of these
functions performs its own READ_ONCE() of the list head. This can lead
to a situation where the list_empty() sees a valid list entry, but the
subsequent list_first() sees a different view of list head state after a
modification.

In the case of dm-thin, this author had a production box crash from a GP
fault in the process_deferred_bios path. This function saw a valid list
head in get_first_thin() but when it subsequently dereferenced that and
turned it into a thin_c, it got the inside of the struct pool, since the
list was now empty and referring to itself. The kernel on which this
occurred printed both a warning about a refcount_t being saturated, and
a UBSAN error for an out-of-bounds cpuid access in the queued spinlock,
prior to the fault itself. When the resulting kdump was examined, it
was possible to see another thread patiently waiting in thin_dtr's
synchronize_rcu.

The thin_dtr call managed to pull the thin_c out of the active thins
list (and have it be the last entry in the active_thins list) at just
the wrong moment which lead to this crash.

Fortunately, the fix here is straight forward. Switch get_first_thin()
function to use l…

Source: NIST National Vulnerability Database NVD GitHub Advisory

References

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