Apache Log4j JSON Template Layout: Improper serialization of non-finite floating-point values in JsonTemplateLayout

MITRE NVD CVE.ORG JSON API Print: PDF PDF

Summary

CVECVE-2026-34481
StatePUBLISHED
Assignerapache
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-10 16:16:31 UTC
Updated2026-04-24 18:24:14 UTC
DescriptionApache 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 containing an attacker-controlled floating-point value. Users are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue.

Risk And Classification

Primary CVSS: v4.0 6.3 MEDIUM from [email protected]

CVSS:4.0/AV:N/AC:H/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

EPSS: 0.001530000 probability, percentile 0.357030000 (date 2026-04-27)

Problem Types: CWE-116 | CWE-116 CWE-116 Improper Encoding or Escaping of Output

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary6.3MEDIUMCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/C...
4.0CNACVSS6.3MEDIUMCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N
3.1[email protected]Primary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
High
Attack Requirements
Present
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
None
Sub Conf.
None
Sub Integrity
Low
Sub Availability
None

CVSS:4.0/AV:N/AC:H/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

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Apache Log4j All All All All
Application Apache Log4j 3.0.0 alpha1 All All
Application Apache Log4j 3.0.0 alpha1_rc1 All All
Application Apache Log4j 3.0.0 alpha1_rc2 All All
Application Apache Log4j 3.0.0 beta1 All All
Application Apache Log4j 3.0.0 beta2 All All
Application Apache Log4j 3.0.0 beta3 All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Apache Software Foundation Apache Log4j JSON Template Layout affected 2.14.0 2.25.4 maven Not specified
CNA Apache Software Foundation Apache Log4j JSON Template Layout affected 3.0.0-alpha1 3.0.0-beta3 maven Not specified

References

ReferenceSourceLinkTags
logging.apache.org/security.html [email protected] logging.apache.org Vendor Advisory
logging.apache.org/log4j/2.x/manual/json-template-layout.html [email protected] logging.apache.org Technical Description
logging.apache.org/cyclonedx/vdr.xml [email protected] logging.apache.org Product
github.com/apache/logging-log4j2/pull/4080 [email protected] github.com Issue Tracking
www.openwall.com/lists/oss-security/2026/04/10/10 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com Mailing List, Third Party Advisory
lists.apache.org/thread/n34zdv00gbkdbzt2rx9rf5mqz6lhopcv [email protected] lists.apache.org Mailing List, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Ap4sh (Samy Medjahed) and Ethicxz (Eliott Laurie) (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-02-16T18:14:00.000ZVulnerability reported by Ap4sh and ethicxz
CNA2026-03-10T20:42:00.000ZCandidate patch internally shared by Piotr P. Karwasz
CNA2026-03-24T23:06:00.000ZFix shared publicly by Piotr P. Karwasz as pull request #4080
CNA2026-03-25T09:54:00.000ZFix verified by the reporter
CNA2026-03-28T11:19:00.000ZLog4j 2.25.4 released
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