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
CWE-ID CWE-835
Exploitation vector Network
Public exploit Public exploit code for vulnerability #1 is available.
Vulnerable software
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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

CVSSv3.1:

CVE-ID: CVE-2021-45105

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

Exploit availability: Yes

Description

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}}}}

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Apache Log4j: 2.8 - 2.16.0


CPE2.3 External links

http://issues.apache.org/jira/browse/LOG4J2-3230
http://logging.apache.org/log4j/2.x/security.html
http://www.zerodayinitiative.com/advisories/ZDI-21-1541/

Q & A

Can this vulnerability be exploited remotely?

Is there known malware, which exploits this vulnerability?



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