KEV Intelligence

Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2021-45046

Apache Log4j Denial of Service

Apache Software Foundation / Apache Log4j · affected before 2.16.0

View live feed Monitor via API
Severity
CVSS 9.0 · Critical
Confidence
Confirmed
Exploit status
Exploited in the wild
EPSS
100.0%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-45046 is an unauthenticated vulnerability affecting Apache Software Foundation Apache Log4j. It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default...

Is it exploited?

Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.

Who is affected?

Apache Software Foundation / Apache Log4j affected before 2.16.0.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Apache Log4j Denial of Service

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.

Vendor Product Affected Status
Apache Software Foundation Apache Log4j Before 2.16.0 Affected
View vendor advisory (opens in new tab)
Published
14 Dec 2021
Exploitation Reported
01 May 2023
Attack vector
Remote
Complexity
High
Privileges
None
User interaction
None

Tags

apache ransomware cisa malware nuclei_scanner java

CVE References

Exploitation evidence

Why KEV Intelligence marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 01 May 2023

Independent exploitation attestation added to the KEV Intelligence record.

Used in malware

CISA

Recorded 01 May 2023

Malware families have been linked to exploitation of this CVE.

Proof of concept available

GitHub

Recorded 15 Dec 2021

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.

Learn about Pro API access
Source Added
CISA First 2023-05-01 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
0
User-Agents
0

Raw values available in Pro and Enterprise.

Virtual patch status

No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-45046.yaml 25 Apr 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.0 Critical
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS

100.0%

Weaknesses

Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') CWE-917

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

Apache Log4j2 - Remote Code Injection

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. Public PoC available

    Public proof-of-concept code published

  2. Nuclei template available

    Scanner coverage available

  3. Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  4. First public exploitation report

    Exploit observed in malware

  5. CVE published

    Vulnerability disclosed publicly

  6. CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

View Pro pricing Read API docs
  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2021-45046

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2021-45046",
  "confidence": "Confirmed",
  "cvss_score": 9.0,
  "cvss_estimated": false,
  "epss_score": 0.99977,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

Early warning alerts

Get alerts on high-impact exploitation

Receive curator-selected alerts when exploitation activity warrants attention. Each alert includes the evidence and context needed to decide what requires attention now.

Occasional high-impact alerts. Unsubscribe anytime. See our Privacy Policy.