oss-security - CVE-2025-68161: Apache Log4j Core: Missing TLS hostname verification in Socket appender

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Message-ID: <8905aefe-dfb9-e198-c1fe-6d6a955b45a9@apache.org>
Date: Thu, 18 Dec 2025 19:09:46 +0000
From: Piotr Karwasz <pkarwasz@...che.org>
To: oss-security@...ts.openwall.com
Subject: CVE-2025-68161: Apache Log4j Core: Missing TLS hostname
 verification in Socket appender 

Severity: moderate 

Affected versions:

- Apache Log4j Core (org.apache.logging.log4j:log4j-core) 2.0-beta9 before 2.25.3

Description:

The Socket Appender in Apache Log4j Core versions 2.0-beta9 through 2.25.2 does not perform TLS hostname verification of the peer certificate, even when the  verifyHostName https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName  configuration attribute or the  log4j2.sslVerifyHostName https://logging.apache.org/log4j/2.x/manual/systemproperties.html#log4j2.sslVerifyHostName  system property is set to true.

This issue may allow a man-in-the-middle attacker to intercept or redirect log traffic under the following conditions:

  *  The attacker is able to intercept or redirect network traffic between the client and the log receiver.
  *  The attacker can present a server certificate issued by a certification authority trusted by the Socket Appender’s configured trust store (or by the default Java trust store if no custom trust store is configured).

Users are advised to upgrade to Apache Log4j Core version 2.25.3, which addresses this issue.

As an alternative mitigation, the Socket Appender may be configured to use a private or restricted trust root to limit the set of trusted certificates.

Credit:

Samuli Leinonen (finder)

References:

https://github.com/apache/logging-log4j2/pull/4002
https://logging.apache.org/security.html#CVE-2025-68161
https://logging.apache.org/cyclonedx/vdr.xml
https://logging.apache.org/log4j/2.x/manual/systemproperties.html#log4j2.sslVerifyHostName
https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName
https://logging.apache.org/
https://www.cve.org/CVERecord?id=CVE-2025-68161

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