Krishna Chidrawar created KAFKA-20957:
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Summary: [CVE-2026-49844] [log4j-api] [2.25.4]
Key: KAFKA-20957
URL: https://issues.apache.org/jira/browse/KAFKA-20957
Project: Kafka
Issue Type: Bug
Reporter: Krishna Chidrawar
*Description :* Improper encoding of non-finite floating-point values during
MapMessage JSON serialization in Apache Log4j API produces output that is not
valid JSON. This issue affects Apache Log4j API versions 2.13.1 through 2.25.4
and version 2.26.0.
The fix for CVE-2026-34481 did not cover all code paths: when a MapMessage
contains a non-finite IEEE 754 value (NaN, Infinity, or -Infinity),
MapMessage.asJson() emits the corresponding bare token. RFC 8259 does not
permit these tokens, so a conformant parser rejects the resulting document.
The defect is reachable only when both of the following conditions hold:
* The application uses the message resolver
[https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message]
of JsonTemplateLayout or any other layout that relies on MapMessage.asJson()
or MapMessage.getFormattedMessage(new String[] \{"JSON"}
).
* The application logs a MapMessage that contains an attacker-controlled
floating-point value.
An attacker who can supply a non-finite value can cause the affected layout to
emit malformed JSON, which may corrupt the enclosing log record or disrupt
downstream log ingestion and parsing.
Users are advised to upgrade to Apache Log4j API 2.25.5 or 2.26.1, both of
which emit RFC 8259-compliant JSON for non-finite values.
*NVD URL :* [https://nvd.nist.gov/vuln/detail/CVE-2026-49844]
*Fix Version :* 2.25.5, 2.26.1
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