Improper input validation in Apache Log4j

Published: 2021-12-15 | Updated: 2021-12-23
Risk High
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2021-45046
Exploitation vector Network
Public exploit Public exploit code for vulnerability #1 is available.
Vulnerable software
Apache Log4j
Universal components / Libraries / Libraries used by multiple products

Vendor Apache Foundation

Security Bulletin

This security bulletin contains information about 1 vulnerabilities.

Updated: 18.12.2021

Raised severity level from Medium to High to reflect remote code execution.

1) Code Injection

EUVDB-ID: #VU58976

Risk: High

CVSSv3.1: 8.1 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2021-45046

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

Exploit availability: Yes


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.


Install updates from vendor's website.

Vulnerable software versions

Apache Log4j: 2.0, 2.0.1, 2.0.2, 2.1, 2.2, 2.3, 2.4, 2.4.1, 2.5, 2.6, 2.6.1, 2.6.2, 2.7, 2.8, 2.8.1, 2.8.2, 2.9.0, 2.9.1, 2.10.0, 2.11.0, 2.11.1, 2.11.2, 2.12.0, 2.12.1, 2.13.0, 2.13.1, 2.13.2, 2.13.3, 2.14.0, 2.14.1, 2.15.0

CPE2.3 External links

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. However, proof of concept for this vulnerability is available.