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

Source

https://github.com/mergebase/log4j-samples

Associated Vulnerability

Title: Apache Log4j2 Thread Context Message Pattern and Context Lookup Pattern vulnerable to a denial of service attack (CVE-2021-45046)
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.

Description

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

Readme


# log4j-samples
Samples of log4j library versions to help log4j scanners / detectors (including our own [log4j-detector](https://github.com/mergebase/log4j-detector)) improve their accuracy for detecting CVE-2021-45046 and CVE-2021-44228.

The samples include shaded jars, [uber jars](https://mergebase.com/blog/software-composition-analysis-sca-vs-java-uber-jars/), spring-boot executable jars, jars inside jars, exploded jars, etc.

# Directory Organization

- [./false-hits/](./false-hits/) - No sample in here is vulnerable to CVE-2021-45046 or CVE-2021-44228.
- [./old-hits/](./old-hits/) - Every sample in here contains versions of Log4J (1.x and 2.x) that are too old to be vulnerable.
- [./true-hits/](./true-hits/) - Every sample in here **is vulnerable** to CVE-2021-45046 and CVE-2021-44228.

# Why Are \*.zip Files Included In The Samples?

Java treats \*.zip exactly the same as \*.jar, and always has. You really don't want attackers to simply rename "webapp/WEB-INF/lib/log4j-core-2.9.jar" to "log4j-core-2.9.zip" to defeat your scanner! Don't believe me?  Try this:

```
$ wget https://github.com/mergebase/log4j-samples/raw/master/false-hits/log4j-detector-2021.12.16.zip
$ java -jar log4j-detector-2021.12.16.zip

Usage: java -jar log4j-detector-2021.12.16.jar [--verbose] [paths to scan...]

Exit codes:  0 = No vulnerable Log4J versions found.
             1 = At least one legacy Log4J 1.x version found.
             2 = At least one vulnerable Log4J 2.x version found.

About - MergeBase log4j detector (version 2021.12.16)
Docs  - https://github.com/mergebase/log4j-detector 
(C) Copyright 2021 Mergebase Software Inc. Licensed to you via GPLv3.
```
(Similarly, this also works: `java -cp log4j-detector-2021.12.16.zip com.mergebase.log4j.Log4JDetector`).


# Latest Scan With [log4j-detector](https://github.com/mergebase/log4j-detector)

```
-- github.com/mergebase/log4j-detector v2021.12.16 (by mergebase.com) analyzing paths (could take a while).
-- Note: specify the '--verbose' flag to have every file examined printed to STDERR.
/opt/mergebase/log4j-samples/false-hits/exploded/2.12.2/org/apache/logging/log4j contains Log4J-2.x   >= 2.12.2 _SAFE_ :-)
/opt/mergebase/log4j-samples/false-hits/log4j-core-2.12.2.jar contains Log4J-2.x   >= 2.12.2 _SAFE_ :-)
/opt/mergebase/log4j-samples/false-hits/log4j-core-2.16.0.jar contains Log4J-2.x   >= 2.16.0 _SAFE_ :-)
/opt/mergebase/log4j-samples/old-hits/log4j-1.1.3.jar contains Log4J-1.x   <= 1.2.17 _OLD_ :-|
/opt/mergebase/log4j-samples/old-hits/log4j-1.2.17.jar contains Log4J-1.x   <= 1.2.17 _OLD_ :-|
/opt/mergebase/log4j-samples/old-hits/log4j-core-2.0-beta2.jar contains Log4J-2.x   <= 2.0-beta8 _POTENTIALLY_SAFE_ :-| (or did you already remove JndiLookup.class?) 
/opt/mergebase/log4j-samples/true-hits/exploded/2.12.1/org/apache/logging/log4j contains Log4J-2.x   >= 2.10.0 _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/log4j-core-2.0-beta9.jar contains Log4J-2.x   >= 2.0-beta9 (< 2.10.0) _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/log4j-core-2.10.0.jar contains Log4J-2.x   >= 2.10.0 _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/log4j-core-2.10.0.zip contains Log4J-2.x   >= 2.10.0 _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/log4j-core-2.15.0.jar contains Log4J-2.x   >= 2.15.0 _OKAY_ :-|
/opt/mergebase/log4j-samples/true-hits/log4j-core-2.9.1.jar contains Log4J-2.x   >= 2.0-beta9 (< 2.10.0) _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/shaded/clt-1.0-SNAPSHOT.jar contains Log4J-2.x   >= 2.10.0 _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/springboot-executable/spiff-0.0.1-SNAPSHOT.ear!/WEB-INF/lib/log4j-core-2.10.0.jar contains Log4J-2.x   >= 2.10.0 _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/springboot-executable/spiff-0.0.1-SNAPSHOT.jar!/WEB-INF/lib/log4j-core-2.10.0.jar contains Log4J-2.x   >= 2.10.0 _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/springboot-executable/spiff-0.0.1-SNAPSHOT.war!/WEB-INF/lib/log4j-core-2.10.0.jar contains Log4J-2.x   >= 2.10.0 _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/springboot-executable/spiff-0.0.1-SNAPSHOT.zip!/WEB-INF/lib/log4j-core-2.10.0.jar contains Log4J-2.x   >= 2.10.0 _VULNERABLE_ :-(
/opt/mergebase/log4j-samples/true-hits/uber/infinispan-embedded-query-8.2.12.Final.jar contains Log4J-2.x   >= 2.0-beta9 (< 2.10.0) _VULNERABLE_ :-(
```

File Snapshot

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