Bug 2499304 (CVE-2026-49844)

Summary:	CVE-2026-49844 org.apache.logging.log4j/log4j-api: Apache Log4j API: Malformed JSON output due to improper encoding of floating-point values
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	aazores, abrianik, alinfoot, anujha, aschwart, asoldano, asyoung, aszczucz, ataylor, bbaranow, bbrownin, bmaxwell, boliveir, bstansbe, chfoley, cmah, csutherl, dbruscin, dhanak, dlofthou, drichtar, drosa, dsimansk, dsoumis, dtrifiro, eaguilar, ebaron, ehugonne, ewittman, fmariani, fmongiar, ggrzybek, gmalinko, istudens, ivassile, iweiss, janstey, jclere, jhollowa, jmatsuok, jnethert, jraez, jtolenti, jwon, kaycoth, kgaikwad, kingland, kvanderr, mcarlett, mnovotny, mosmerov, mposolda, msvehla, nipatil, nwallace, pantinor, parichar, pberan, pesilva, pjindal, plodge, pmackay, prichard, rbryant, rgodfrey, rhel-process-autobot, rkubis, rmartinc, rmaucher, rstancel, rstepani, sausingh, sdawley, ssilvert, sthirugn, sthorger, swoodman, szappis, tasato, tcunning, thjenkin, vdosoudi, vmuzikar, watson-tool-maintainers, weaton, yfang
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in Apache Log4j API. This vulnerability occurs due to improper encoding of non-finite floating-point values during JSON serialization of MapMessages, leading to invalid JSON output. An attacker who can supply a non-finite value can exploit this to cause the affected logging layout to emit malformed JSON. This can corrupt log records or disrupt downstream log ingestion and parsing, potentially leading to a Denial of Service (DoS) or information integrity issues.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-07-10 22:04:43 UTC

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.