Vulnerability identifier: #VU59051

Vulnerability risk: Medium

CVSSv3.1:

CVE-ID: CVE-2021-45105

CWE-ID: CWE-835

Exploitation vector: Network

Exploit availability: Yes

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

Vendor: Apache Foundation

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

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CPE

• cpe:2.3:a:apache_foundation:log4j:2.16.0:*:*:*:*:*:*:*

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/

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Q & A

Can this vulnerability be exploited remotely?

Is there known malware, which exploits this vulnerability?