Answer in brief
CVE-2026-34481 records a High severity (CVSS 7.5) vulnerability in Apache Log4j JSON Template Layout: Improper serialization of non-finite floating-point values in JsonTemplateLayout. The current sources do not mark it as known exploited. The current feed maps Apache Software Foundation/Apache Log4j JSON Template Layout (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2026-34481 records a High severity (CVSS 7.5) vulnerability in Apache Log4j JSON Template Layout: Improper serialization of non-finite floating-point values in JsonTemplateLayout. The current sources do not mark it as known exploited. The current feed maps Apache Software Foundation/Apache Log4j JSON Template Layout (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Apache Software Foundation/Apache Log4j JSON Template Layout (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Apache Software Foundation/Apache Log4j JSON Template Layoutgeneric | >=2.14.0 <2.25.4 || 3.0.0-alpha1 | 2.25.4 |
Published upstream
Apr 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 11, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 11, 2026
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, or logs an object directly (e.g., via Logger.info(Object), which wraps it in an ObjectMessage), where the message contains an attacker-controlled floating-point value. Users are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue. Note: The fix released in version 2.25.4 did not cover all affected code paths. CVE-2026-49844 was assigned to the remaining issue, which concerns the MapMessage.asJson() serialization in Apache Log4j API and is fixed in versions 2.25.5 and 2.26.1.
Quoted source text, attributed separately from HOL analysis.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Apache Software Foundation/Apache Log4j JSON Template Layout (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Apache Software Foundation/Apache Log4j JSON Template Layoutgeneric | >=2.14.0 <2.25.4 || 3.0.0-alpha1 | 2.25.4 |
Published upstream
Apr 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 11, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 11, 2026
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, or logs an object directly (e.g., via Logger.info(Object), which wraps it in an ObjectMessage), where the message contains an attacker-controlled floating-point value. Users are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue. Note: The fix released in version 2.25.4 did not cover all affected code paths. CVE-2026-49844 was assigned to the remaining issue, which concerns the MapMessage.asJson() serialization in Apache Log4j API and is fixed in versions 2.25.5 and 2.26.1.
Quoted source text, attributed separately from HOL analysis.