Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2026-34479— Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters

Quick assessment

Affected
Apache Software Foundation Apache Log4j 1 to Log4j 2 bridge
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存在安全漏洞，该漏洞源于Log4j1XmlLayout未能转义XML 1.0标准禁止的字符，可能产生格式错误的XML输出。

AI Predicted 5.3 Difficulty: Easy EPSS 0.91% · P59

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-34479

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters
Source: CVE Program / CVE List V5
Vulnerability Description
The Log4j1XmlLayout from the Apache Log4j 1-to-Log4j 2 bridge fails to escape characters forbidden by the XML 1.0 standard, producing malformed XML output. Conforming XML parsers are required to reject documents containing such characters with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records. Two groups of users are affected: * Those using Log4j1XmlLayout directly in a Log4j Core 2 configuration file. * Those using the Log4j 1 configuration compatibility layer with org.apache.log4j.xml.XMLLayout specified as the layout class. Users are advised to upgrade to Apache Log4j 1-to-Log4j 2 bridge version 2.25.4, which corrects this issue. Note: The Apache Log4j 1-to-Log4j 2 bridge is deprecated and will not be present in Log4j 3. Users are encouraged to consult the Log4j 1 to Log4j 2 migration guide https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html , and specifically the section on eliminating reliance on the bridge.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/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存在安全漏洞，该漏洞源于Log4j1XmlLayout未能转义XML 1.0标准禁止的字符，可能产生格式错误的XML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 1 to Log4j 2 bridge 2.7 ~ 2.25.4 cpe:2.3:a:apache:log4j_1_2_api:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-34479

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-34479

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-34479 (1)

Mailing List Discussions for CVE-2026-34479 (1)

Vendor Pages for CVE-2026-34479 (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-2026-34481 Apache Log4j JSON Template Layout: Improper serialization of non-finite floating-point val
CVE-2026-34480 Apache Log4j Core: Silent log event loss in XmlLayout due to unescaped XML 1.0 forbidden c
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-2026-34479

No comments yet

Leave a comment