Advisory Details

December 19th, 2021

Apache Log4j StrSubstitutor Uncontrolled Recursion Denial-of-Service Vulnerability

ZDI-21-1541
ZDI-CAN-16160

CVE ID CVE-2021-45105
CVSS SCORE 5.3, AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
AFFECTED VENDORS Apache
AFFECTED PRODUCTS Log4j
VULNERABILITY DETAILS

This vulnerability allows remote attackers to create a denial-of-service condition on affected installations of Apache Log4j. Authentication is not required to exploit this vulnerability.

The specific flaw exists within the StrSubstitutor class. The issue results from the lack of proper validation of user-supplied data, which can result in a resource exhaustion condition. An attacker can leverage this vulnerability to create a denial-of-service condition on the process.

ADDITIONAL DETAILS Apache has issued an update to correct this vulnerability. More details can be found at:
https://logging.apache.org/log4j/2.x/security.html
DISCLOSURE TIMELINE
  • 2021-12-15 - Vulnerability reported to vendor
  • 2021-12-19 - Coordinated public release of advisory
CREDIT Guy Lederfein of Trend Micro Security Research
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