CVE-2026-49844

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.
Configurations

Configuration 1 (hide)

OR cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:2.26.0:*:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:3.0.0:alpha1:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc1:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc2:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:3.0.0:beta1:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:3.0.0:beta2:*:*:*:*:*:*

History

14 Jul 2026, 20:03

Type Values Removed Values Added
First Time Apache
Apache log4j
CVSS v2 : unknown
v3 : unknown
v2 : unknown
v3 : 5.9
References () https://github.com/apache/logging-log4j2/pull/4163 - () https://github.com/apache/logging-log4j2/pull/4163 - Issue Tracking, Patch
References () https://logging.apache.org/cyclonedx/vdr.xml - () https://logging.apache.org/cyclonedx/vdr.xml - Vendor Advisory
References () https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message - () https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message - Product
References () https://logging.apache.org/security.html#CVE-2026-49844 - () https://logging.apache.org/security.html#CVE-2026-49844 - Vendor Advisory
CPE cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc2:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:2.26.0:*:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:3.0.0:alpha1:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc1:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:3.0.0:beta1:*:*:*:*:*:*
cpe:2.3:a:apache:log4j:3.0.0:beta2:*:*:*:*:*:*

10 Jul 2026, 22:16

Type Values Removed Values Added
New CVE

Information

Published : 2026-07-10 22:16

Updated : 2026-07-14 20:03


NVD link : CVE-2026-49844

Mitre link : CVE-2026-49844

CVE.ORG link : CVE-2026-49844


JSON object : View

Products Affected

apache

  • log4j
CWE
CWE-116

Improper Encoding or Escaping of Output