GHSA-6HG6-V5C8-FPHQ

Vulnerability from github – Published: 2026-04-10 18:31 – Updated: 2026-04-14 00:11
VLAI?
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 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.

Severity ?
6.3 (Medium)
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
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.apache.logging.log4j:log4j-core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.12.0"
            },
            {
              "fixed": "2.25.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.apache.logging.log4j:log4j-core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0-alpha1"
            },
            {
              "last_affected": "3.0.0-beta3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-34477"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-297"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-14T00:11:55Z",
    "nvd_published_at": "2026-04-10T16:16:30Z",
    "severity": "MODERATE"
  },
  "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 `\u003cSsl\u003e` 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 \u003cSsl\u003e element.\n  *  The attacker can present a certificate issued by a CA trusted by the appender\u0027s 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.",
  "id": "GHSA-6hg6-v5c8-fphq",
  "modified": "2026-04-14T00:11:55Z",
  "published": "2026-04-10T18:31:17Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Apache Log4j Core: `verifyHostName` attribute silently ignored in TLS configuration"
}


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