Improper input validation in Apache Log4j

1) Code Injection

EUVDB-ID: #VU58976

Risk: High

CVSSv3.1: 8.6 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H/E:H/RL:O/RC:C]

CVE-ID: CVE-2021-45046

CWE-ID: CWE-94 - Improper Control of Generation of Code ('Code Injection')

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to incomplete patch in Apache Log4j 2.15.0 for a code injection vulnerability #VU58816 (CVE-2021-44228) in certain non-default configurations. A remote attacker with control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout with either a Context Lookup (for example, $${ctx:loginId}) or a Thread Context Map pattern (%X, %mdc, or %MDC) can pass malicious data using a JNDI Lookup pattern and perform a denial of service (DoS) attack, exfiltrate data or execute arbitrary code.

Later discovery demonstrates a remote code execution on macOS but no other tested environments.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Apache Log4j: 2.0 - 2.15.0

External links

http://www.openwall.com/lists/oss-security/2021/12/14/4
http://logging.apache.org/log4j/2.x/security.html
http://www.cve.org/CVERecord?id=CVE-2021-44228
http://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00646.html
http://issues.apache.org/jira/browse/LOG4J2-3221

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?

Yes. This vulnerability is being exploited in the wild.