CVE-2026-34477: Apache Log4j Core `verifyHostName` Attribute Silently Ignored Vulnerability

MODERATE
Advisory Identifier: GHSA-6hg6-v5c8-fphq
Share
CWE-297
Published
Advisory Summary

CVE-2026-34477 is a MODERATE `verifyhostname` attribute silently ignored vulnerability (CWE-297: Improper Validation of Certificate with Host Mismatch) affecting Apache Log4j Core libraries in the Maven ecosystem. The issue involves `verifyhostname` attribute silently ignored in tls configuration. Remediation is available by upgrading affected packages to version 2.25.4.

CVE-2026-34477 at a Glance

CVE Identifier CVE-2026-34477
GHSA Identifier GHSA-6hg6-v5c8-fphq
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-297: Improper Validation of Certificate with Host Mismatch
Affected Product Apache Log4j Core
Package Ecosystem Maven
Published Date
Last Updated

How to Fix CVE-2026-34477

To remediate this vulnerability, upgrade all affected Apache Log4j Core dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

org.apache.logging.log4j:log4j-core fixed: 2.25.4 
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.25.4</version>
</dependency>
org.apache.logging.log4j:log4j-core fixed: Latest secure release 
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>Latest secure release</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=org.apache.logging.log4j

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-34477, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.apache.logging.log4j

Analyze the terminal output to locate any version of Apache Log4j Core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.25.4), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.apache.logging.log4j command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-297: Improper Validation of Certificate with Host Mismatch, where the product communicates with a host that provides a certificate, but the product does not properly ensure that the certificate is actually associated with that host. In Apache Log4j Core, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2026-34477 Affected Apache Log4j Core Versions

2 component(s)
Fixed Versions:
2.25.4
Product / Package Ecosystem Affected Versions Fixed Version
org.apache.logging.log4j:log4j-core
maven/org.apache.logging.log4j/log4j-core
Maven
≥ 2.12.0
< 2.25.4
2.25.4
org.apache.logging.log4j:log4j-core
maven/org.apache.logging.log4j/log4j-core
Maven
≥ 3.0.0-alpha1
≤ 3.0.0-beta3

References

NVD — CVE-2026-34477 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-34477
Apache Log4j Core Source Repository REPOSITORY
https://github.com/apache/logging-log4j2/pull/4075
Apache Log4j Core Source Repository REPOSITORY
https://github.com/apache/logging-log4j2
lists.apache.org/thread/lkx8cl46t2bv... WEB
https://lists.apache.org/thread/lkx8cl46t2bvkcwfcb2pd43ygc097lq4
logging.apache.org/cyclonedx/vdr.xml WEB
https://logging.apache.org/cyclonedx/vdr.xml
logging.apache.org/log4j/2.x/manual/ap... WEB
https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName
Apache Log4j Core Security Information SECURITY
https://logging.apache.org/security.html#CVE-2026-34477

Frequently Asked Questions

What is CVE-2026-34477?
CVE-2026-34477 is a security vulnerability in Apache Log4j Core involving `verifyHostName` attribute silently ignored in TLS configuration under CWE-297: Improper Validation of Certificate with Host Mismatch.
Which Apache Log4j Core versions are affected?
Affected versions include releases prior to 2.25.4 across affected packages: org.apache.logging.log4j:log4j-core.
What version fixes CVE-2026-34477?
Upgrading to 2.25.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is log4j-core affected?
Yes, org.apache.logging.log4j:log4j-core is affected in releases prior to 2.25.4, Latest secure release. Upgrade your dependency to 2.25.4, Latest secure release or later.
What CWE is associated with CVE-2026-34477?
CVE-2026-34477 is classified under CWE-297: Improper Validation of Certificate with Host Mismatch (The product communicates with a host that provides a certificate, but the product does not properly ensure that the certificate is actually associated with that host.).
How can I check Maven dependencies for CVE-2026-34477?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.apache.logging.log4j'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6hg6-v5c8-fphq",
  "modified" : "2026-04-14T00:11:55Z",
  "published" : "2026-04-10T18:31:17Z",
  "aliases" : [ "CVE-2026-34477" ],
  "summary" : "Apache Log4j Core: `verifyHostName` attribute silently ignored in TLS configuration",
  "details" : "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.\n\nAlthough 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.\n\nA network-based attacker may be able to perform a man-in-the-middle attack when all of the following conditions are met:\n\n  *  An SMTP, Socket, or Syslog appender is in use.\n  *  TLS is configured via a nested <Ssl> element.\n  *  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.\n\nThis 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.\n\nUsers are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.apache.logging.log4j:log4j-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.12.0"
      }, {
        "fixed" : "2.25.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.apache.logging.log4j:log4j-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.0.0-alpha1"
      }, {
        "last_affected" : "3.0.0-beta3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-34477"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/apache/logging-log4j2/pull/4075"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/apache/logging-log4j2"
  }, {
    "type" : "WEB",
    "url" : "https://lists.apache.org/thread/lkx8cl46t2bvkcwfcb2pd43ygc097lq4"
  }, {
    "type" : "WEB",
    "url" : "https://logging.apache.org/cyclonedx/vdr.xml"
  }, {
    "type" : "WEB",
    "url" : "https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName"
  }, {
    "type" : "WEB",
    "url" : "https://logging.apache.org/security.html#CVE-2026-34477"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-297" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-14T00:11:55Z",
    "nvd_published_at" : "2026-04-10T16:16:30Z"
  }
}