CVE-2021-4104Network attack vector

Authenticated code execution via JMSAppender JNDI lookups

Published Dec 14, 2021 · Updated May 28, 2026

Deserialization in Apache Log4j 1.2 JMSAppender allows remote authenticated users to execute code through crafted JNDI bindings. JMSAppender uses attacker-controlled TopicBindingName and TopicConnectionFactoryBindingName values in JNDI lookups that deserialize untrusted data. Exploitation requires write access to the Log4j configuration and the non-default JMSAppender configuration; successful exploitation executes code in the hosting Java process.

CVSS severity7.5
High
EPSS probability81.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Deserialization in Apache Log4j 1.2 JMSAppender allows remote authenticated users to execute code through crafted JNDI bindings. JMSAppender uses attacker-controlled TopicBindingName and TopicConnectionFactoryBindingName values in JNDI lookups that deserialize untrusted data. Exploitation requires write access to the Log4j configuration and the non-default JMSAppender configuration; successful exploitation executes code in the hosting Java process.

The record

CVE
CVE-2021-4104
Published
Dec 14, 2021
Updated
May 28, 2026
Vendor
The Apache Software Foundation
Product
Apache Log4j
Classifications
CWE-502
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 14, 2021CVE publishedPublication date reported by the CVE source.
  2. May 28, 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.

  1. Affected versionversion=Apache Log4j 1.2 1.2.x

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Apache Software Foundation · Apache Log4jversion=Apache Log4j 1.2 1.2.x

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
6.0NIST NVDAV:N/AC:M/Au:S/C:P/I:P/A:P
7.5CISA-ADPCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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