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Low severityNVD Advisory· Published Apr 27, 2020· Updated Aug 4, 2024

CVE-2020-9488

CVE-2020-9488

Description

Improper validation of certificate with host mismatch in Apache Log4j SMTP appender. This could allow an SMTPS connection to be intercepted by a man-in-the-middle attack which could leak any log messages sent through that appender. Fixed in Apache Log4j 2.12.3 and 2.13.1

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Apache Log4j SMTP appender fails to validate SMTPS certificate hostnames, enabling man-in-the-middle attacks that leak log messages; fixed in 2.12.3 and 2.13.1.

Root

Cause

The Apache Log4j SMTP appender did not validate that the hostname of the SMTPS server matched the SSL/TLS certificate presented during the connection handshake [1]. This missing hostname verification is a classic instance of improper certificate validation (CWE-297) [2].

Exploitation

An attacker with a man-in-the-middle position on the network between the Log4j application and the SMTPS server can intercept the encrypted connection. By presenting a valid certificate for a different host, the attacker can decrypt and read all log messages transmitted through that appender [1]. No authentication is required; network access is the primary prerequisite [2].

Impact

The attacker gains the ability to read sensitive log data transmitted via SMTPS. The confidentiality impact is limited to the contents of log messages, which may include authentication credentials, session tokens, or other sensitive information depending on the application's logging practices [2].

Mitigation

Apache Log4j versions 2.12.3 and 2.13.1 include a fix that enables SSL configuration with hostname verification [1]. Users unable to upgrade can set the system property mail.smtp.ssl.checkserveridentity to true to enable global hostname verification for SMTPS connections [2].

References
  1. NVD - CVE-2020-9488
  2. [LOG4J2-2819] Add support for specifying an SSL configuration for SmtpAppender

AI Insight generated on May 21, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
org.apache.logging.log4j:log4jMaven
>= 2.13.0, < 2.13.22.13.2
org.apache.logging.log4j:log4j-coreMaven
>= 2.13.0, < 2.13.22.13.2
org.apache.logging.log4j:log4jMaven
>= 2.4.0, < 2.12.32.12.3
org.apache.logging.log4j:log4jMaven
< 2.3.22.3.2
org.apache.logging.log4j:log4j-coreMaven
>= 2.4.0, < 2.12.32.12.3
org.apache.logging.log4j:log4j-coreMaven
< 2.3.22.3.2

Affected products

3

Patches

0

No patches discovered yet.

Vulnerability mechanics

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References

91

News mentions

0

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