#VU58977 Deserialization of Untrusted Data in Apache Log4j - CVE-2021-4104

Vulnerability identifier: #VU58977

Vulnerability risk: Medium

CVSSv4.0: 7.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-4104

CWE-ID: CWE-502

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Apache Log4j
Universal components / Libraries / Libraries used by multiple products

Vendor: Apache Foundation

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to insecure input validation when processing serialized data in JMSAppender, 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.

Note this issue only affects Log4j 1.2 when specifically configured to use JMSAppender, which is not the default.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Apache Log4j: 1.2.1 - 1.2.17

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External links
https://access.redhat.com/security/cve/CVE-2021-4104
https://www.cve.org/CVERecord?id=CVE-2021-44228
https://github.com/apache/logging-log4j2/pull/608#issuecomment-990494126

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.