Vulnerability · Published Apr 10, 2026 · Assigned by apache
CVE-2026-34477Apache Log4j Core: verifyHostName attribute silently ignored in TLS configuration, allowing hostname verification bypass
Medium 6.3
In plain English
A medium-severity security flaw in Apache Log4j Core from Apache Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
The fix for CVE-2025-68161 https://logging.apache.org/security.html#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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Maven | org.apache.logging.log4j:log4j-core | 2.25.4 | GHSA-6hg6-v5c8-fphq |
| Maven | org.apache.logging.log4j:log4j-core | no fix listed | GHSA-6hg6-v5c8-fphq |
| Ubuntu:22.04:LTS | apache-log4j2 | no fix listed | UBUNTU-CVE-2026-34477 |
| Ubuntu:24.04:LTS | apache-log4j2 | no fix listed | UBUNTU-CVE-2026-34477 |
| Ubuntu:25.10 | apache-log4j2 | no fix listed | UBUNTU-CVE-2026-34477 |
| Ubuntu:26.04:LTS | apache-log4j2 | no fix listed | UBUNTU-CVE-2026-34477 |
| Ubuntu:26.10 | apache-log4j2 | no fix listed | UBUNTU-CVE-2026-34477 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Apache Software Foundation | Apache Log4j Core | 2.12.0 – before 2.25.43.0.0-alpha1 – through 3.0.0-beta3 |
Weakness: CWE-297 · Vector: 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
References
- https://github.com/apache/logging-log4j2/pull/4075 patch
- https://logging.apache.org/security.html#CVE-2026-34477 vendor-advisory
- https://logging.apache.org/cyclonedx/vdr.xml vendor-advisory
- https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName related
- https://lists.apache.org/thread/lkx8cl46t2bvkcwfcb2pd43ygc097lq4 vendor-advisory