Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in versions up to and including 2.25.3, produces invalid JSON output when log events contain non-finite floating-point values (NaN, Infinity, or -Infinity), which are prohibited by RFC 8259. This may cause downstream log processing systems to reject or fail to index affected records. An attacker can exploit this issue only if both of the following conditions are met:
* The application uses JsonTemplateLayout.
* The application logs a MapMessage containing an attacker-controlled floating-point value.
Users are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Attack Requirements
Present
Additional conditions required
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
References 6
https://github.com/apache/logging-log4j2/pull/4080
security@apache.org
https://lists.apache.org/thread/n34zdv00gbkdbzt2rx9rf5mqz6lhopcv
security@apache.org
https://logging.apache.org/cyclonedx/vdr.xml
security@apache.org
https://logging.apache.org/log4j/2.x/manual/json-template-layout.html
security@apache.org
https://logging.apache.org/security.html#CVE-2026-34481
security@apache.org
http://www.openwall.com/lists/oss-security/2026/04/10/10
af854a3a-2127-422b-91ae-364da2661108