6.3

CVE-2026-49844

Apache Log4j API: Improper serialization of non-finite floating-point values in MapMessage.asJson()

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.
Daten sind bereitgestellt durch National Vulnerability Database (NVD)
Apache ≫ Log4j Version >= 2.13.1 < 2.25.5
Apache ≫ Log4j Version2.26.0
Apache ≫ Log4j Version3.0.0 Updatealpha1
Apache ≫ Log4j Version3.0.0 Updatealpha1_rc1
Apache ≫ Log4j Version3.0.0 Updatealpha1_rc2
Apache ≫ Log4j Version3.0.0 Updatebeta1
Apache ≫ Log4j Version3.0.0 Updatebeta2
VulnDex Vulnerability Enrichment
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Zu dieser CVE wurde keine Warnung gefunden.
EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 0.57% 0.439
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
NIST 5.9 2.2 3.6
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Apache 6.3 0 0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CWE-116 Improper Encoding or Escaping of Output

The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.

https://logging.apache.org/cyclonedx/vdr.xml
Vendor Advisory
https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message
Product
https://github.com/apache/logging-log4j2/pull/4163
Patch
Issue Tracking
https://logging.apache.org/security.html#CVE-2026-49844
Vendor Advisory