Answer in brief
CVE-2026-49844 records a Medium severity (CVSS 6.3) vulnerability in Apache Log4j API: Improper serialization of non-finite floating-point values in MapMessage.asJson(). The current sources do not mark it as known exploited. The current feed maps Apache Software Foundation/Apache Log4j API (generic), org.apache.logging.log4j:log4j-api (maven), org.apache.logging.log4j:log4j-api (maven), org.apache.logging.log4j:log4j-api (maven) and additional mapped packages. 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 6.3. 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 API (generic), org.apache.logging.log4j:log4j-api (maven), org.apache.logging.log4j:log4j-api (maven), org.apache.logging.log4j:log4j-api (maven) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:a:apache:log4j:2.26.0:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:a:apache:log4j:3.0.0:alpha1:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc1:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc2:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:a:apache:log4j:3.0.0:beta1:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:a:apache:log4j:3.0.0:beta2:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Apache Software Foundation/Apache Log4j APIgeneric | >=2.13.1 <2.25.5 || >=2.26.0 <2.26.1 || 3.0.0-alpha1 | 2.25.5, 2.26.1 |
| org.apache.logging.log4j:log4j-apimaven | >=2.13.1 <2.25.5 | 2.25.5 |
| org.apache.logging.log4j:log4j-apimaven | >=2.26.0 <2.26.1 | 2.26.1 |
| org.apache.logging.log4j:log4j-apimaven | >=2.13.1,<2.25.5 | 2.25.5 |
| org.apache.logging.log4j:log4j-apimaven | >=2.26.0,<2.26.1 | 2.26.1 |
Published upstream
Jul 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 25, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 10, 2026
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.
Quoted source text, attributed separately from HOL analysis.