7.5

CVE-2026-34481: apache software foundation apache log4j json template layout Improper Encoding or Escaping of Output

CVSS: 7.5v3.1HighModified
AliasesUBUNTU-CVE-2026-34481DEBIAN-CVE-2026-34481CGA-28fm-p367-5pgw
Published 10-04-2026Last modified 11-07-2026
Open JSON

Vulnerability summary

CVE-2026-34481 is a high (CVSS 7.5) Improper Encoding or Escaping of Output vulnerability in apache software foundation apache log4j json template layout. EPSS estimates a 0.85% chance of exploitation in the next 30 days, higher than 57.5% of scored vulnerabilities.

Overall risk
30/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.5/10
010
High · v3.1 (NVD)
EPSS score
0.85%
0%100%
Low · +0.16 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 1 · Related 2
OPENSUSE-SU-2026:10544-1CGA-JFGG-24J2-8JCC

Timeline

  1. 10-04-2026
    PublishedVulnerability first disclosed.
  2. 11-07-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

9 scores · 7 sources · 2 versions

EPSS trend

Probability

0.85%

Chance of exploitation in the next 30 days

Percentile

58%

Versus all other CVEs

30-day change

+0.16 pp

From 0.69% on 18-09-2026

18-09-202618-10-2026
EPSS score
0.85%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard50 products
  • apache-camel-karavan-devmode< 4.14.2-r8
  • apache-pulsar-4.0< 4.0.9-r11
  • apache-pulsar-4.1All versions (No fix recorded)
  • apache-pulsar-4.2< 4.2.1-r0
  • apache-pulsar-fips-4.0< 4.0.9-r11
Wolfi24 products
  • apache-pulsar-4.1All versions (No fix recorded)
  • apache-pulsar-4.2< 4.2.1-r0
  • flink-2.1< 2.1.1-r5
  • flink-2.2< 2.2.0-r5
  • kafka_exporter-strimzi-compat< 1.2.0-r5
Ubuntu2 products
  • apache-log4j1.2All versions (No fix recorded)
  • apache-log4j2All versions (No fix recorded)
Apache1 product
  • log4j≥ 2.14.0, < 2.25.4 | 3.0.0:alpha1 | 3.0.0:alpha1_rc1 | 3.0.0:alpha1_rc2 | 3.0.0:beta1 | 3.0.0:beta2 | 3.0.0:beta3
Apache software foundation1 product
Debian1 product
  • apache-log4j2All versions (No fix recorded)
Org.apache.logging.log4j1 product
  • log4j-layout-template-json≥ 2.14.0, < 2.25.4 | ≥ 3.0.0-alpha1, ≤ 3.0.0-beta3

7 vendors · 80 products

References

13 links
Show all 13 references