TLS interception via ignored hostname verification attribute
Published Apr 10, 2026 · Updated Apr 10, 2026
Improper certificate validation in Apache Log4j Core allows man-in-the-middle attackers to intercept appender TLS traffic. The SslConfiguration plugin factory uses a legacy overload that drops the nested Ssl element’s verifyHostName value, so certificates for the wrong host are accepted. Exploitation requires an SMTP, Socket, or Syslog appender using that TLS element and a certificate from its configured or default Java trust store; the HTTP appender is unaffected.
Summary
What happened
Improper certificate validation in Apache Log4j Core allows man-in-the-middle attackers to intercept appender TLS traffic. The SslConfiguration plugin factory uses a legacy overload that drops the nested Ssl element’s verifyHostName value, so certificates for the wrong host are accepted. Exploitation requires an SMTP, Socket, or Syslog appender using that TLS element and a certificate from its configured or default Java trust store; the HTTP appender is unaffected.
The record
- CVE
- CVE-2026-34477
- Published
- Apr 10, 2026
- Updated
- Apr 10, 2026
- Vendor
- The Apache Software Foundation
- Product
- Apache Log4j Core
- Classifications
- CWE-297, CWE-295, T1557
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 10, 2026CVE publishedPublication date reported by the CVE source.
- Apr 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.12.0 <2.25.4
- Affected versionversion=3.0.0-alpha1 <=3.0.0-beta3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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