Improper Encoding or Escaping of Output Affecting org.apache.logging.log4j:log4j-core package, versions [2.7, 2.25.4)[3.0.0-alpha1,]
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applicationsSnyk Learn
Learn about Improper Encoding or Escaping of Output vulnerabilities in an interactive lesson.
Start learning- Snyk IDSNYK-JAVA-ORGAPACHELOGGINGLOG4J-15967804
- published10 Apr 2026
- disclosed10 Apr 2026
- creditSamy Medjahed, Eliott Laurie, jabaltarik1
Introduced: 10 Apr 2026
NewCVE-2026-34479 (opens in a new tab)How to fix?
A fix was pushed into the master branch but not yet published.
Overview
org.apache.logging.log4j:log4j-core is a logging library for Java.
Affected versions of this package are vulnerable to Improper Encoding or Escaping of Output in the Log4j1XmlLayout plugin. An attacker can cause log events to be silently lost or downstream log processing systems to drop or fail to index affected records by introducing XML 1.0 forbidden characters into log messages, resulting in malformed XML output that conforming XML parsers reject with a fatal error.