Improper Certificate Validation
CVE-2026-34477
Summary
The fix for CVE-2025-68161 was incomplete: it addressed hostname verification only when enabled via the "log4j2.sslVerifyHostName" system property, but not when configured through the "verifyHostName" attribute of the "<Ssl>" element. Although the "verifyHostName" configuration attribute was introduced in Log4j Core 2.12.0, it was silently ignored in all versions through 2.25.3, leaving TLS connections vulnerable to interception regardless of the configured value. A network-based attacker may be able to perform a man-in-the-middle attack when all of the following conditions are met: An SMTP, Socket, or Syslog appender is in use. TLS is configured via a nested element. The attacker can present a certificate issued by a CA trusted by the appender's configured trust store, or by the default Java trust store if none is configured. This issue does not affect users of the HTTP appender, which uses a separate verifyHostname attribute that was not subject to this bug and verifies host names by default. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue. Versions 2.12.0 prior to 2.25.4 and all 3.x versions are affected.
- HIGH
- NETWORK
- HIGH
- UNCHANGED
- NONE
- NONE
- NONE
- NONE
CWE-295 - Improper Certificate Validation
The authenticity component of a web system stems from the ability to validate “Digital certificates”, which (i) establish trust between two or more entities sharing data over a network; (ii) ensure data at rest and transit is secure from unauthorized access; and (iii) check the identity of the actors that interact with the system. An application with absent or ineffective certificate validation mechanisms allows malicious users, impersonating trusted hosts, to manipulate the communication path between the client and the host, resulting in unauthorized access to data and to the application’s internal environment, and potentially enabling man-in-the-middle attacks.
References
Advisory Timeline
- Published
