CVE-2026-34477

Description

The fix for CVE-2025-68161 was incomplete: it addressed hostname verification only when enabled via the [`log4j2.sslVerifyHostName`](https://logging.apache.org/log4j/2.x/manual/systemproperties.html#log4j2.sslVerifyHostName) system property, but not when configured through the [`verifyHostName`](https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-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 <Ssl> 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`](https://logging.apache.org/log4j/2.x/manual/appenders/network.html#HttpAppender-attr-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.

How to fix CVE-2026-34477

To remediate CVE-2026-34477, upgrade the affected package to a fixed version below.

—upgrade to 2.25.4 or later

Is CVE-2026-34477 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

>= 2.12.0, < 2.25.4

CVSS scores

Source	Version	Severity	Vector
osv	CVSS 4.0	—	CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:L/SA:N