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Fencer Vulns
high 7.5

CVE-2026-34481 json

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

published 2026-04-10 6 mo ago modified 2026-10-26 13 d ago also GHSA-w35j-pv5h-q9q9 , EUVD-2026-21412

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits
0
none known

Summary

Apache 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, or logs an object directly (e.g., via Logger.info(Object), which wraps it in an ObjectMessage), where the message contains an attacker-controlled floating-point value.

Users are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue.

Note: The fix released in version 2.25.4 did not cover all affected code paths. CVE-2026-49844 was assigned to the remaining issue, which concerns the MapMessage.asJson() serialization in Apache Log4j API and is fixed in versions 2.25.5 and 2.26.1.

Patch / fix

  • maven org.apache.logging.log4j:log4j-layout-template-json 2.25.4
  • Apache Software Foundation Apache Log4j JSON Template Layout 2.25.4
  • log4j openSUSE Tumbleweed 2.20.0-2.1

opensuse advisories openSUSE-SU-2026:10544-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-34481 updated cvss 6.5

org.apache.logging.log4j: Apache Log4j JsonTemplateLayout: Denial of Service via invalid JSON output

  • Red Hat Enterprise Linux 9 log4j, log4j-jcl, log4j-slf4j Red Hat JBoss Enterprise Application Platform 7 log4j-layout-template-json
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Offline Knowledge Portal redhat-user-workloads/rhocc-mimir-tenant/mimir/rhokp-core-encrypted
    affected: workaround, no fix available
  • Red Hat AMQ Broker 7.13.6
    fixed: vendor fix RHSA-2026:66545
  • Red Hat AMQ Broker 7.14.1
    fixed: vendor fix RHSA-2026:66488
  • Red Hat build of Apache Camel 4.18.1.P1 for Spring Boot 3.5.16
    fixed: vendor fix RHSA-2026:37390
  • Red Hat Data Grid 8.6.1
    fixed: vendor fix RHSA-2026:22619
  • Red Hat Offline Knowledge Portal 1.2.13 offline-knowledge-portal/rhokp-rhel9 1779996999
    fixed: vendor fix RHSA-2026:21773
  • Red Hat Streams for Apache Kafka 3.2.1
    fixed: vendor fix RHSA-2026:54435
show 1 more
  • Red Hat Enterprise Linux 8 log4j, log4j-jcl, log4j-web, log4j-slf4j Red Hat JBoss Enterprise Application Platform 8 log4j-layout-template-json Red Hat JBoss Enterprise Application Platform Expansion Pack log4j-layout-template-json
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.72% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 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
CNA 4.0 6.3 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
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
maven org.apache.logging.log4j:log4j-layout-template-json
>=2.14.0, <2.25.4
>=3.0.0-alpha1, <=3.0.0-beta3
2.25.4

Affected products

  • Apache Software Foundation Apache Log4j JSON Template Layout

Classification

Weakness
  • CWE-116 Improper Encoding or Escaping of Output
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.