Vulnerability in Kernel (CVE-2025-21909)

Summary

Vulnerability in Kernel (CVE-2025-21909). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 5.4.291, 5.10.235, 5.15.179, 6.1.131, 6.6.83, 6.12.19, 6.13.7 or later.

Original description

The description as published by the source.

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

wifi: nl80211: reject cooked mode if it is set along with other flags

It is possible to set both MONITOR_FLAG_COOK_FRAMES and MONITOR_FLAG_ACTIVE
flags simultaneously on the same monitor interface from the userspace. This
causes a sub-interface to be created with no IEEE80211_SDATA_IN_DRIVER bit
set because the monitor interface is in the cooked state and it takes
precedence over all other states. When the interface is then being deleted
the kernel calls WARN_ONCE() from check_sdata_in_driver() because of missing
that bit.

Fix this by rejecting MONITOR_FLAG_COOK_FRAMES if it is set along with
other flags.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Source: OSV.dev (Open Source Vulnerabilities) NVD OSV

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-2025-21909 has been found in Kernel.
Risk of unauthorized operations or information disclosure.
What to do: upgrade Kernel to 5.4.291, 5.10.235, 5.15.179, 6.1.131, 6.6.83, 6.12.19, 6.13.7 or later.
If unsure, ask your IT team or search "Kernel CVE-2025-21909" on the vendor's site.

CVE-2025-21909 (Kernel)
Patched: 5.4.291, 5.10.235, 5.15.179, 6.1.131, 6.6.83, 6.12.19, 6.13.7 — apply immediately
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 Kernel.

📍 Affected scope

Check the vendor advisory for the affected versions of Kernel.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 5.4.291, 5.10.235, 5.15.179, 6.1.131, 6.6.83, 6.12.19, 6.13.7.

🛡️ 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. Run grep -r 'Kernel' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'Kernel' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Kernel を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade Kernel to 5.4.291, 5.10.235, 5.15.179, 6.1.131, 6.6.83, 6.12.19, 6.13.7
```
ステージング環境で 5.4.291, 5.10.235, 5.15.179, 6.1.131, 6.6.83, 6.12.19, 6.13.7 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
3
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。

Affected packages

Linux Kernel

[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.26"},{"fixed":"5.4.291"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.5.0"},{"fixed":"5.10.235"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.179"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.131"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.83"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.19"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.13.7"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

BellSoft Alpaquita BELL-CVE-2025-21909 linux-lts Fixed in: 6.1.131-r0
Debian DEBIAN-CVE-2025-21909 linux Fixed in: 5.10.237-1
Ubuntu UBUNTU-CVE-2025-21909 linux