What is the CVSS score of CVE-2021-45046?

CVE-2021-45046 has a CVSS 3.1 base score of 9.0 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H. EPSS exploitation probability: 94.3%.

Is there a public PoC exploit available for CVE-2021-45046?

Yes, a public proof-of-concept exploit is available for CVE-2021-45046. Prioritise patching immediately. EPSS: 94.3%.

How to fix or mitigate CVE-2021-45046?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. Vendor patch is available.

Apache Log4j CVE-2021-45046

CRITICAL

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

2021-12-14 security@apache.org

GHSA-7rjr-3q55-vv33

9.0

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-917 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V14 - Configuration Dependency management, component inventory
Impact	Critical risk (CVSS 9.0, EPSS 94.3%). While the non-default configuration requirement limits scope compared to the original Log4Shell, many enterprise applications use MDC/Context logging patterns, especially in multi-tenant and authentication-logging scenarios.
Exploit ScenarioDerived	An application using Log4j 2.15.0 (patched for Log4Shell) uses ${ctx:userId} in its log pattern. An attacker submits a login with username containing a JNDI payload. The MDC captures the username, and when logged, the lookup bypass achieves code execution despite the initial patch.

Act Now Prioritize within 24-48h. Why: In CISA KEV with patch available.

Exploited in the wild (CISA KEV) Patch available 94.3% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 26, 2026

Apache Log4j2 contains an incomplete fix for Log4Shell (CVE-2021-44228) that allows attackers to bypass the initial patch through Thread Context Map (MDC) input data in non-default configurations, enabling RCE and DoS.

Earlier versions of this analysis (1)

v1 Mar 26, 2026 - 11:19 CVSS 9.0

The fix for CVE-2021-44228 in Log4j 2.15.0 was incomplete in non-default configurations. Attackers can still achieve code execution through Thread Context Map (MDC) data when specific Pattern Layout configurations are used.

RemediationAI

Update to Log4j 2.17.1+ (the fully patched version). Log4j 2.16.0 disabled JNDI by default but had additional issues. Only 2.17.1+ is considered fully secure.

Affected Packages

maven org.apache.logging.log4j:log4j-core fix: 2.3.1, 2.12.2, 2.16.0

maven org.ops4j.pax.logging:pax-logging-log4j2 fix: 1.9.2, 1.10.8, 1.11.11, 2.0.12

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in maven

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The CWE-917 OGNL/EL injection bypass works when logging configurations use Context Lookup patterns (${ctx:loginId}) or Thread Context Map patterns in their Pattern Layout. In these configurations, Log4j 2.15.0's restrictions on JNDI lookups can be circumvented through MDC-injected data.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.0 CRITICAL

AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Added to CISA KEV

Oct 27, 2025 - 17:35 cisa

CISA KEV

Patch released

Oct 27, 2025 - 17:35 nvd

Patch available

CVE Published

Dec 14, 2021 - 19:15 nvd

CRITICAL 9.0

DescriptionCVE.org

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.

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

598 maven packages depend on org.apache.logging.log4j:log4j-core (254 direct, 347 indirect)

Ecosystem-wide dependent count for version 2.13.0.

Executive ViewAI

Why It Matters

CVE-2021-45046 presents critical security risk rated CVSS 9.0. Successful exploitation could critically impact the confidentiality, integrity, and availability of affected systems. This vulnerability is actively exploited in the wild (KEV-listed) and requires immediate remediation. A patch is available and should be applied immediately given the critical severity.

Business Impact: Severe

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.

Threat Intelligence Overview

Threat Score

9.6/10

Composite threat intelligence

EPSS Score

94.3%

Top 0% exploitable

Threat Intel

1 sources

Exploit

POC

Public exploit code exists

Data Quality

5 sources

Confidence: Medium

NVD

CVE.org

CISA KEV

EPSS GHSA POC (3) THREAT

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV Yes

Public POC Yes

EPSS 94.3%

Patch available Yes

Active threat Yes

Deciding rule

In CISA KEV with patch available

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.