CVE-2021-45105
Apache Log4j2 does not always protect from infinite recursion in lookup evaluation
- Published
- Dec 18, 2021
- Updated
- May 29, 2026
- Assigning CNA
- apache
- Evidence observed
- Aug 23, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HHigh · next 30 days
- Percentile
- 100.0%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
Apache Log4j2 versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) did not protect from uncontrolled recursion from self-referential lookups. This allows an attacker with control over Thread Context Map data to cause a denial of service when a crafted string is interpreted. This issue was fixed in Log4j 2.17.0, 2.12.3, and 2.3.1.
Sources
11PoC exploit for CVE-2021-45105 (Log4j2 DOS) with Spring Boot web app, demonstrating infinite loop via crafted HTTP header/body payloads.
- Log4ShellRemediationResearch
A vulnerable Spring Boot application that uses log4j and is vulnerable to CVE-2021-44228, CVE-2021-44832, CVE-2021-45046 and CVE-2021-45105
Sample Spring Boot web application vulnerable to Log4j2 CVE-2021-45105 with documented exploitation steps and mitigation guidance for security testing and education.
Responsible use
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