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CVE-2021-45046 CISA KEV high

[KEV] Unsafe Deserialization in org.apache.logging.log4j:log4j-core (CVE-2021-45046)

Summary

Vulnerability in org.apache.logging.log4j:log4j-core (CVE-2021-45046). Successful exploitation can lead to full system takeover. Listed in CISA KEV — actively exploited. Mitigation: upgrade to 2.3.1 or later.

Original description

The description as published by the source.

Impact

The fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allow attackers with control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout with either a Context Lookup (for example, $${ctx:loginId}) or a Thread Context Map pattern (%X, %mdc, or %MDC) to craft malicious input data using a JNDI Lookup pattern resulting in a remote code execution (RCE) attack.

Affected packages

Only the org.apache.logging.log4j:log4j-core package is directly affected by this vulnerability. The org.apache.logging.log4j:log4j-api should be kept at the same version as the org.apache.logging.log4j:log4j-core package to ensure compatability if in use.

Mitigation

Log4j 2.16.0 fixes this issue by removing support for message lookup patterns and disabling JNDI functionality by default. This issue can be mitigated in prior releases (< 2.16.0) by removing the JndiLookup class from the classpath (example: zip -q -d log4j-core-*.jar org/apache/logging/log4j/core/lookup/JndiLookup.class).

Log4j 2.15.0 restricts JNDI LDAP lookups to localhost by default. Note that previous mitigations involving configuration such as to set the system property log4j2.formatMsgNoLookups to true do NOT mitigate this specific vulnerability.

Source: CISA Known Exploited Vulnerabilities NVD GitHub Advisory 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-2021-45046 has been found in org.apache.logging.log4j:log4j-core.
Successful exploitation can lead to full system takeover.
Note: CISA has officially confirmed this is actively exploited in the wild. Treat it with elevated urgency.
What to do: upgrade org.apache.logging.log4j:log4j-core to 2.3.1 or later.
If unsure, ask your IT team or search "org.apache.logging.log4j:log4j-core CVE-2021-45046" on the vendor's site.

CVE-2021-45046 (org.apache.logging.log4j:log4j-core) — CWE-502
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 2.3.1 — apply immediately
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

Unsafe deserialization (CWE-502) exists in org.apache.logging.log4j:log4j-core.

📍 Affected scope

Check the vendor advisory for the affected versions of org.apache.logging.log4j:log4j-core.

🔥 Severity

Severity: High. 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 2.3.1.

🛡️ 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 org.apache.logging.log4j:log4j-core を使っているサービスとバージョンを洗い出す。

  2. 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. 3
    Apply patch patch 
    Upgrade org.apache.logging.log4j:log4j-core to 2.3.1

    ステージング環境で 2.3.1 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。

  4. 4
    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

maven org.apache.logging.log4j:log4j-core
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.1"}]}]
maven org.ops4j.pax.logging:pax-logging-log4j2
[{"type":"ECOSYSTEM","events":[{"introduced":"2.0.0"},{"fixed":"2.0.12"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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