Is CVE-2021-4104 actively exploited?

Yes. CVE-2021-4104 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, which means exploitation in the wild has been confirmed.

Can CVE-2021-4104 be exploited remotely?

The attack vector of CVE-2021-4104 has not been classified yet.

What is the CVSS score of CVE-2021-4104?

CVE-2021-4104 has not received a CVSS score yet.

HOME VULNERABILITIESCVE-2021-4104

UNKNOWNCISA KEVIN THE WILD

CVE-2021-4104

Published: April 11, 2026

EPSS:69.28%probability of exploitation in 30 daysPercentile:98.6th

Official Description

JMSAppender in Log4j 1.2 is vulnerable to deserialization of untrusted data when the attacker has write access to the Log4j configuration. The attacker can provide TopicBindingName and TopicConnectionFactoryBindingName configurations causing JMSAppender to perform JNDI requests that result in remote code execution in a similar fashion to CVE-2021-44228. Note this issue only affects Log4j 1.2 when specifically configured to use JMSAppender, which is not the default. Apache Log4j 1.2 reached end of life in August 2015. Users should upgrade to Log4j 2 as it addresses numerous other issues from the previous versions.

NVD Source

Technical Analysis

CVE-2021-4104 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

CISA has added CVE-2021-4104 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.