Apache Log4j 2 Vulnerabilities (CVE-2021-44228, CVE-2021-45046, CVE-2021-45105 & CVE-2021-44832)

The Apache Software Foundation has released a security advisory to address a Remote Code Execution vulnerability (CVE-2021-44228, CVE-2021-45046 & CVE-2021-44832) & Denial of Service (CVE-2021-45105) being actively exploited in the wild.  A remote attacker could exploit these vulnerabilities to take control of an affected system.  Log4j is an open-source, Java-based logging utility widely used by enterprise applications and cloud services.  System administrator should take remediation immediately.

Vulnerabilities

• CVE-2021-44228, CVE-2021-45046 & CVE-2021-44832 (Remote Code Execution Vulnerability)

Apache Log4j versions between 2 and 2.14.1 JNDI features used in configuration, log messages, and parameters do not protect against attacker controlled LDAP and other JNDI related endpoints.  Attacker who can control log messages or log message parameters can

• • execute arbitrary code loaded from LDAP servers when message lookup substitution is enabled.  From log4j 2.15.0, this behavior has been disabled by default.

However, Apache Log4j 2.15.0 was incomplete in certain non-default configurations.  It could allow attackers with

• • control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout with a Context Lookup (for example, $${ctx:loginId}) to craft malicious input data using a JNDI Lookup pattern, resulting in an information leak and remote code execution in some environments and local code execution in all environments.  Log4j 2.16.0 fixes this issue by removing the message lookups feature.

Another finding in Apache Log4j2 versions 2.0-beta7 through 2.17.0 which are vulnerable to a remote code execution (RCE) attack where:

• • an attacker with permission to modify the logging configuration file can construct a malicious configuration using a JDBC Appender with a data source referencing a JNDI URI which can execute remote code.  This issue is fixed by limiting JNDI data source names to the java protocol in Log4j2 versions 2.17.1, 2.12.4, and 2.3.2.
• CVE-2021-45105 (Denial of Service Vulnerability)

It was found that Apache Log4j2 versions 2.0-alpha1 through 2.16.0 did not protect from uncontrolled recursion from self-referential lookups.  This could

• • allow attackers with control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout either with a Context Lookup (for example, $${ctx:loginId}) to craft malicious input data that contains a recursive lookup, resulting in a StackOverflowError that will terminate the process.  this is also known as denial of service (DOS) attack.  This issue was fixed in Log4j 2.17.0, 2.12.3 and 2.3.1.

Severity Level

• Critical

Affected Systems & Remediation

(1) Products confirmed affected:

(2) Products still under evaluation:

(3) Products which can detect the vulnerability:

Reference

• Apache Log4j Security Vulnerabilities:
  https://logging.apache.org/log4j/2.x/security.html
• HKCERT:
  https://www.hkcert.org/security-bulletin/java-se-remote-code-execution-vulnerability_20211210
• USCERT:
  https://www.cisa.gov/uscert/ncas/alerts/aa21-356a
• Australia CERT:
  https://www.cyber.gov.au/acsc/view-all-content/alerts/critical-remote-code-execution-vulnerability-found-apache-log4j2-library
• NIST:
  https://nvd.nist.gov/vuln/detail/CVE-2021-44228
  https://nvd.nist.gov/vuln/detail/CVE-2021-45046
  https://nvd.nist.gov/vuln/detail/CVE-2021-45105
  https://nvd.nist.gov/vuln/detail/CVE-2021-44832
• Microsoft’s Response to CVE-2021-44228 Apache Log4j 2 – Microsoft Security Response Center
  https://msrc-blog.microsoft.com/2021/12/11/microsofts-response-to-cve-2021-44228-apache-log4j2/
• Guidance for preventing, detecting, and hunting for CVE-2021-44228 Log4j 2 exploitation – Microsoft Security Blog
  https://www.microsoft.com/security/blog/2021/12/11/guidance-for-preventing-detecting-and-hunting-for-cve-2021-44228-log4j-2-exploitation/
• Palo Alto Networks — CVE-2021-44228 Informational: Impact of Log4j Vulnerability CVE-2021-44228
  https://security.paloaltonetworks.com/CVE-2021-44228
• Log4j2 Vulnerability | FortiGuard
  https://www.fortiguard.com/outbreak-alert/log4j2-vulnerability

Enquiry

• ITSC Service Desk: http://servicedesk.itsc.cuhk.edu.hk

Published on: 11 Dec 2021

Last update on: 30 Dec 2021