Improper Encoding or Escaping of Output Affecting org.apache.logging.log4j:log4j-api package, versions [2.13.1,2.25.5)[2.26.0,2.26.1)[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.
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Test your applications- Snyk IDSNYK-JAVA-ORGAPACHELOGGINGLOG4J-17954276
- published12 Jul 2026
- disclosed10 Jul 2026
- creditHimanshu Anand
Introduced: 10 Jul 2026
NewCVE-2026-49844 (opens in a new tab)How to fix?
A fix was pushed into the master branch but not yet published.
Overview
Affected versions of this package are vulnerable to Improper Encoding or Escaping of Output in the MapMessage.asJson() method, which emits the bare NaN, Infinity, or -Infinity tokens instead of an RFC 8259-compliant representation. An attacker can emit malformed JSON that corrupts the enclosing log record or disrupts downstream log ingestion and parsing by supplying non-finite floating-point values that the application records in a logged MapMessage. Exploitation requires the application to use the message resolver of JsonTemplateLayout, or another layout relying on MapMessage.asJson(), and to log a MapMessage holding attacker-controlled floating-point values.
Note: This is a bypass of the fix for the vulnerability described in CVE-2026-34481.