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CVE-2021-45046 — It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete…

Key facts

CVE-2021-45046 is a Critical (9.0) vulnerability: It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete…. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2023-05-01), confirming active exploitation in the wild, and is linked to known ransomware campaigns.

Actively exploited — on the CISA KEV catalog

CVE-2021-45046 is listed on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2023-05-01), confirming exploitation in the wild. It is linked to known ransomware campaigns. Federal remediation deadline: 2023-05-22. Prioritise patching and deploy the detection and prevention rules below.
CVE CVE-2021-45046
Severity Critical (9.0)
CISA KEV Actively exploited (added 2023-05-01) · ransomware
Detection / prevention —
PoC poc.py
Source 2021/CVE-2021-45046/

Details

English | 한국어

Description

It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allows 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 an information leak and remote code execution in some environments and local code execution in all environments. Log4j 2.16.0 (Java 8) and 2.12.2 (Java 7) fix this issue by removing support for message lookup patterns and disabling JNDI functionality by default.

Vulnerability Details

Property Value
CVE ID CVE-2021-45046
Type RCE
CVSS Score 9.0

Proof of Concept

Download

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2021/CVE-2021-45046/poc.py

Usage

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start

# Clone and navigate to CVE directory
cd CVE-2021-45046

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints

Application URL Status
Vulnerable App http://localhost:8080 Shows vulnerability
Patched App http://localhost:8081 Demonstrates fix

Directory Structure

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References

  • http://www.openwall.com/lists/oss-security/2021/12/14/4
  • http://www.openwall.com/lists/oss-security/2021/12/15/3
  • http://www.openwall.com/lists/oss-security/2021/12/18/1
  • https://cert-portal.siemens.com/productcert/pdf/ssa-397453.pdf
  • https://cert-portal.siemens.com/productcert/pdf/ssa-479842.pdf
  • https://cert-portal.siemens.com/productcert/pdf/ssa-661247.pdf
  • https://cert-portal.siemens.com/productcert/pdf/ssa-714170.pdf
  • https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EOKPQGV24RRBBI4TBZUDQMM4MEH7MXCY/
  • https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SIG7FZULMNK2XF6FZRU4VWYDQXNMUGAJ/
  • https://logging.apache.org/log4j/2.x/security.html
  • https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0032
  • https://security.gentoo.org/glsa/202310-16
  • https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-log4j-qRuKNEbd
  • https://www.cve.org/CVERecord?id=CVE-2021-44228
  • https://www.debian.org/security/2021/dsa-5022
  • https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00646.html
  • https://www.kb.cert.org/vuls/id/930724
  • https://www.oracle.com/security-alerts/alert-cve-2021-44228.html
  • https://www.oracle.com/security-alerts/cpuapr2022.html
  • https://www.oracle.com/security-alerts/cpujan2022.html
  • https://www.oracle.com/security-alerts/cpujul2022.html
  • http://www.openwall.com/lists/oss-security/2021/12/14/4
  • http://www.openwall.com/lists/oss-security/2021/12/15/3
  • http://www.openwall.com/lists/oss-security/2021/12/18/1
  • https://cert-portal.siemens.com/productcert/pdf/ssa-397453.pdf
  • https://cert-portal.siemens.com/productcert/pdf/ssa-479842.pdf
  • https://cert-portal.siemens.com/productcert/pdf/ssa-661247.pdf
  • https://cert-portal.siemens.com/productcert/pdf/ssa-714170.pdf
  • https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EOKPQGV24RRBBI4TBZUDQMM4MEH7MXCY/
  • https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SIG7FZULMNK2XF6FZRU4VWYDQXNMUGAJ/
  • https://logging.apache.org/log4j/2.x/security.html
  • https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0032
  • https://security.gentoo.org/glsa/202310-16
  • https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-log4j-qRuKNEbd
  • https://www.cve.org/CVERecord?id=CVE-2021-44228
  • https://www.debian.org/security/2021/dsa-5022
  • https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00646.html
  • https://www.kb.cert.org/vuls/id/930724
  • https://www.oracle.com/security-alerts/alert-cve-2021-44228.html
  • https://www.oracle.com/security-alerts/cpuapr2022.html
  • https://www.oracle.com/security-alerts/cpujan2022.html
  • https://www.oracle.com/security-alerts/cpujul2022.html
  • https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-45046

Generated by PoC Generator on 2026-07-08T21:39:39.865805627

Frequently asked questions

What is CVE-2021-45046?

CVE-2021-45046 is a Critical (9.0) vulnerability: It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete…. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2023-05-01), confirming active exploitation in the wild, and is linked to known ransomware campaigns.

How do I detect CVE-2021-45046?

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2021-45046?

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

Is CVE-2021-45046 actively exploited?

Yes. CVE-2021-45046 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2023-05-01, which means it has been exploited in the wild. CISA also links it to known ransomware campaigns. CISA set a federal remediation deadline of 2023-05-22. Prioritise patching and deploy the detection and prevention rules above.

For authorized security testing and research only. See the full source and NVD record.