Infinite recursion in Apache Log4j

Published: 2021-12-18 | Updated: 2021-12-23
Risk Medium
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2021-45105
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 one medium risk vulnerability.

1) Infinite loop

EUVDB-ID: #VU59051

Risk: Medium


CVE-ID: CVE-2021-45105

CWE-ID: CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')

Exploit availability: Yes


The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to infinite loop within the StrSubstitutor class. A remote attacker can pass specially crafted input to the application, consume all available system resources and cause denial of service conditions.

Payload example: ${${::-${::-$${::-j}}}}


Install updates from vendor's website.

Vulnerable software versions

Apache Log4j: 2.8 - 2.16.0

CPE2.3 External links

Q & A

Can this vulnerability be exploited remotely?

Is there known malware, which exploits this vulnerability?