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Log4jFramework / library · Apache

CVE-2026-34477

MEDIUM · 5.9 CVSS v3.1 Published 2026-04-10
Fix available
A fix is available. Upgrade to 2.25.4 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Log4jFramework / library
Affected:>= 2.12.0, < 2.25.4= 3.0.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.25.4 or later
Fixed in 2.25.4
Vendor patch github.com →
Recommended fix High confidence

Apache Log4j Core 2.25.4

  1. Identify the current Log4j Core version in use by checking project dependencies (e.g., pom.xml, build.gradle, or JAR manifest)
  2. Locate all Log4j dependencies across the application and transitive dependencies to ensure complete coverage
  3. Upgrade Apache Log4j Core to version 2.25.4 or later by updating the dependency version in the project's build configuration
  4. If using Maven, add or update the dependency in pom.xml: <groupId>org.apache.logging.log4j</groupId><artifactId>log4j-core</artifactId><version>2.25.4</version>
  5. If using Gradle, update the dependency: implementation 'org.apache.logging.log4j:log4j-core:2.25.4'
  6. Rebuild and redeploy the application
  7. Verify that the upgrade does not break existing functionality by running integration and unit tests
  8. Confirm the fix by reviewing the SslConfiguration attribute handling in the updated Log4j library
Caveat No significant breaking changes expected; this is a bugfix release addressing a security vulnerability, but validate SSL/TLS configurations still work as expected after upgrade

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

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Peer-ranked notes from engineers who’ve handled CVE-2026-34477 in production — separate from our analysis above.

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