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    CVE-2026-34479

    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.

    Published:Apr 10, 2026
    Last Modified:May 6, 2026
    EPS:Apr 10, 2026
    EPSS Score:0.00157
    CVSS Score:7.5

    Affected Products

    Vendor
    Apache
    Product
    Log4j
    Vendor
    Apache
    Product
    Log4j 1 2 Api

    Exploits

    https://github.com/apache/logging-log4j2/pull/4078

    Related CVEs

    CVE-2026-34481 (CVSS 6.3) — Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in …
    CVE-2026-34480 (CVSS 6.9) — Apache Log4j Core's XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in version…
    CVE-2026-34478 (CVSS 6.9) — Apache Log4j Core's Rfc5424Layout https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , in…
    CVE-2026-34477 (CVSS 6.3) — The fix for CVE-2025-68161 https://logging.apache.org/security.html#CVE-2025-68161 was incomplete: it addres…
    CVE-2025-68161 (CVSS 6.3) — The Socket Appender in Apache Log4j Core versions 2.0-beta9 through 2.25.2 does not perform TLS hostname verif…
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    CVE-2022-23302 (CVSS 8.8) — JMSSink in all versions of Log4j 1.x is vulnerable to deserialization of untrusted data when the attacker has …
    CVE-2022-23307 (CVSS 8.8) — CVE-2020-9493 identified a deserialization issue that was present in Apache Chainsaw. Prior to Chainsaw V2.0 C…
    CVE-2021-44832 (CVSS 6.6) — Apache Log4j2 versions 2.0-beta7 through 2.17.0 (excluding security fix releases 2.3.2 and 2.12.4) are vulnera…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High