Out-of-Bounds Write in Linux Kernel (CVE-2021-22555, CVSS 8.3, KEV)

Summary

Out-of-bounds write in Linux Kernel (CVE-2021-22555). Successful exploitation can lead to full system takeover. Listed in CISA KEV — actively exploited.

Original description

The description as published by the source.

Linux Kernel contains a heap out-of-bounds write vulnerability that could allow an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space.

Source: CISA Known Exploited Vulnerabilities NVD CISA KEV

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-2021-22555 has been found in Linux Kernel.
Successful exploitation can lead to full system takeover. CVSS score: 8.3/10.
Note: CISA has officially confirmed this is actively exploited in the wild. Treat it with elevated urgency.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux Kernel CVE-2021-22555" on the vendor's site.

CVE-2021-22555 (Linux Kernel) — CWE-787 / CVSS v3 8.3
Attack vector: adjacent-network / unauthenticated / no user interaction
Listed in CISA KEV — actively exploited, treat as top priority.
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

Out-of-bounds write (CWE-787) exists in Linux Kernel.

📍 Affected scope

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

🔥 Severity

Severity: High (CVSS 8.3/10). Successful exploitation can lead to full system takeover. Listed in CISA KEV — actively exploited in the wild, treat as top priority.

🔧 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. 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
Consider incident declaration escalate
```
Notify SOC / on-call
```
CISA KEV登録済 = 実環境で悪用が観測されている。侵入の兆候があればインシデント対応宣言、無くてもパッチ適用までWAF強化を最優先で。
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。

Fix status by distribution

Fixed packages published by each distribution for this CVE

Ubuntu UBUNTU-CVE-2021-22555 linux Fixed in: 3.13.0-187.238

[KEV] Out-of-Bounds Write in Linux Kernel (CVE-2021-22555)

Summary

Original description

Auto-generated summary

Response actions

Fix status by distribution

References