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CVE-2021-45046— Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack

Quick assessment

Affected
Apache Software Foundation Apache Log4j
Exploitation
Confirmed exploitation in the wild; remediate immediately
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Apache Log4j是美国阿帕奇（Apache）基金会的一款基于Java的开源日志记录工具。 Apache Log4j 2.15.0版本存在代码问题漏洞，该漏洞源于当日志配置使用非默认模式布局和上下文查找或线程上下文映射模式使用 JNDI 查找模式制作恶意输入数据，从而导致拒绝服务攻击。

AI Predicted 9.0 Difficulty: Easy KEV · Ransomware EPSS 99.98% · P100
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I. Basic Information for CVE-2021-45046

Vulnerability Information
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Vulnerability Title
Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
表达式语言语句中使用的特殊元素转义处理不恰当(表达式语言注入)
Source: CVE Program / CVE List V5
Vulnerability Title
Apache Log4j 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Apache Log4j是美国阿帕奇（Apache）基金会的一款基于Java的开源日志记录工具。 Apache Log4j 2.15.0版本存在代码问题漏洞，该漏洞源于当日志配置使用非默认模式布局和上下文查找或线程上下文映射模式使用 JNDI 查找模式制作恶意输入数据，从而导致拒绝服务攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
Apache Software Foundation Apache Log4j Apache Log4j2 ~ 2.16.0 -

II. Public POCs for CVE-2021-45046

# POC Description Source Link Shenlong Link
1 Windows Server Log4j Scanner - Powershell - CVE-2021-45046 and CVE-2021-44228 https://github.com/X1pe0/Log4J-Scan-Win POC Details
2 Log4j 2.15.0 Privilege Escalation -- CVE-2021-45046 https://github.com/cckuailong/Log4j_CVE-2021-45046 POC Details
3 Oh no another one https://github.com/BobTheShoplifter/CVE-2021-45046-Info POC Details
4 Replicating CVE-2021-45046 https://github.com/tejas-nagchandi/CVE-2021-45046 POC Details
5 None https://github.com/pravin-pp/log4j2-CVE-2021-45046 POC Details
6 Public testing data. Samples of log4j library versions to help log4j scanners / detectors improve their accuracy for detecting CVE-2021-45046 and CVE-2021-44228. TAG_TESTING, OWNER_KEN, DC_PUBLIC https://github.com/mergebase/log4j-samples POC Details
7 A simple script to remove Log4J JndiLookup.class from jars in a given directory, to temporarily protect from CVE-2021-45046 and CVE-2021-44228. https://github.com/lukepasek/log4jjndilookupremove POC Details
8 None https://github.com/ludy-dev/cve-2021-45046 POC Details
9 Log4j 漏洞本地检测脚本。 Scan all java processes on your host to check whether it's affected by log4j2 remote code execution vulnerability (CVE-2021-45046) https://github.com/lijiejie/log4j2_vul_local_scanner POC Details
10 Log4Shell(CVE-2021-45046) Sandbox Signature https://github.com/CaptanMoss/Log4Shell-Sandbox-Signature POC Details
11 None https://github.com/shaily29-eng/CyberSecurity_CVE-2021-45046 POC Details
12 Apache Log4j2 Thread Context Lookup Pattern is vulnerable to remote code execution in certain non-default configurations. https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-45046.yaml POC Details
13 Apache Log4j2 Thread Context Lookup Pattern is vulnerable to remote code execution in certain non-default configurations. https://github.com/projectdiscovery/nuclei-templates/blob/main/dast/cves/2021/CVE-2021-45046.yaml POC Details
14 Apache Log4j2 Thread Context Lookup Pattern is vulnerable to remote code execution in certain non-default configurations. https://github.com/projectdiscovery/nuclei-templates/blob/main/dast/cves/2021/CVE-2021-45046-DAST.yaml POC Details
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III. Intelligence Information for CVE-2021-45046

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Vendor Advisories for CVE-2021-45046 (13)

Mailing List Discussions for CVE-2021-45046 (5)

Other References for CVE-2021-45046 (3)

Same Patch Batch · Apache Software Foundation · 2021-12-14 · 3 CVEs total

CVE-2021-4104 Deserialization of untrusted data in JMSAppender in Apache Log4j 1.2
CVE-2021-44549 SMTPS server hostname not checked when making TLS connection to SMTPS server

IV. Related Vulnerabilities

Same product: Apache Log4j
Same vendor: Apache Software Foundation
Same weakness: CWE-917

V. Comments for CVE-2021-45046

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