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CVE-2026-34481— Apache Log4j JSON Template Layout: Improper serialization of non-finite floating-point values in JsonTemplateLayout

Quick assessment

Affected
Apache Software Foundation Apache Log4j JSON Template Layout
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Apache Log4j是美国阿帕奇（Apache）基金会的一款基于Java的开源日志记录工具。 Apache Log4j JSON Template Layout 2.25.3及之前版本存在安全漏洞，该漏洞源于JsonTemplateLayout在日志事件包含非有限浮点值时产生无效的JSON输出。

AI Predicted 5.3 Difficulty: Trivial EPSS 0.85% · P57

Possible ATT&CK Techniques 1 AI

T1078 · Valid Accounts

Affected Version Matrix 2

VendorProduct Version RangeStatus
Apache Software Foundation Apache Log4j JSON Template Layout 2.14.0< 2.25.4 affected
3.0.0-alpha1≤ 3.0.0-beta3 affected
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I. Basic Information for CVE-2026-34481

Vulnerability Information
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Vulnerability Title
Apache Log4j JSON Template Layout: Improper serialization of non-finite floating-point values in JsonTemplateLayout
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
对输出编码和转义不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Apache Log4j 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Apache Log4j是美国阿帕奇（Apache）基金会的一款基于Java的开源日志记录工具。 Apache Log4j JSON Template Layout 2.25.3及之前版本存在安全漏洞，该漏洞源于JsonTemplateLayout在日志事件包含非有限浮点值时产生无效的JSON输出。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Apache Software Foundation Apache Log4j JSON Template Layout 2.14.0 ~ 2.25.4 cpe:2.3:a:apache:log4j_layout_template_json:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-34481

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III. Intelligence Information for CVE-2026-34481

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Patches & Fixes for CVE-2026-34481 (1)

Mailing List Discussions for CVE-2026-34481 (1)

Same Patch Batch · Apache Software Foundation · 2026-04-10 · 8 CVEs total

CVE-2026-40023 Apache Log4cxx, Apache Log4cxx (Conan), Apache Log4cxx (Brew): Silent log event loss in XM
CVE-2026-40021 Apache Log4net: Silent log event loss in XmlLayout and XmlLayoutSchemaLog4J due to unescap
CVE-2026-34480 Apache Log4j Core: Silent log event loss in XmlLayout due to unescaped XML 1.0 forbidden c
CVE-2026-34479 Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescape
CVE-2026-34478 Apache Log4j Core: Log injection in Rfc5424Layout due to silent configuration incompatibil
CVE-2026-34477 Apache Log4j Core: verifyHostName attribute silently ignored in TLS configuration, allowin
CVE-2026-39304 Apache ActiveMQ Client, Apache ActiveMQ Broker, Apache ActiveMQ All, Apache ActiveMQ: Inco

IV. Related Vulnerabilities

Same vendor: Apache Software Foundation
Same weakness: CWE-116

V. Comments for CVE-2026-34481

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