Log4j-core-2.6.1.jar: Security Vulnerabilities

log4j-core-2.6.1.jar, a core component of the Apache Log4j library, has been identified with several security vulnerabilities. This article provides a comprehensive overview of these vulnerabilities, their potential impact, and the recommended remediation steps. Understanding these issues is crucial for anyone using this library, as it can significantly affect the security posture of your applications. We will explore each vulnerability in detail, providing context, technical specifics, and actionable advice to protect your systems. The findings are based on the analysis of the log4j-core-2.6.1.jar file and its associated dependencies within the Monica-Barajas_1114_015203_gh_gw2 repository, focusing on the identified CVEs and their implications.

Overview of the Vulnerabilities

This section offers a detailed breakdown of the vulnerabilities associated with log4j-core-2.6.1.jar. The vulnerabilities are presented with their severity levels, CVSS scores, exploit maturity, and EPSS (Exploit Prediction Scoring System) scores, alongside links to the respective CVE (Common Vulnerabilities and Exposures) databases for further information. The provided table summarizes the critical information at a glance, allowing readers to quickly assess the risks. The findings highlight the importance of timely patching and version upgrades to mitigate these risks. Detailed analysis of each vulnerability, its impact, and recommended solutions are given below.

Detailed Analysis of Vulnerabilities

This section dives into the specifics of each identified vulnerability, providing a detailed breakdown of each CVE. It covers the vulnerability description, its potential impact, and the recommended solutions.

CVE-2021-44228: The Critical Remote Code Execution Vulnerability

CVE-2021-44228 represents a severe security flaw within log4j-core-2.6.1.jar. The vulnerability allows for remote code execution (RCE) due to the way Log4j handles JNDI (Java Naming and Directory Interface) lookups. Attackers can exploit this by crafting malicious input that, when processed by the vulnerable Log4j version, results in the execution of arbitrary code loaded from remote servers. This can lead to complete system compromise, data breaches, and other significant security incidents. This vulnerability highlights the importance of keeping software up-to-date and following secure coding practices.

• Vulnerability Details: Apache Log4j2 versions 2.0-beta9 through 2.15.0 (excluding security releases 2.12.2, 2.12.3, and 2.3.1) are susceptible to this attack. The issue arises from the JNDI features used in configurations, log messages, and parameters, which fail to protect against attacker-controlled LDAP and other JNDI-related endpoints. When message lookup substitution is enabled, an attacker who controls log messages or parameters can execute code loaded from LDAP servers.
• Threat Assessment: The exploit maturity is rated as High, with an EPSS score of 94.4%, indicating a high likelihood of exploitation.
• Suggested Fix: The recommended solution is to upgrade to a patched version. The suggested fix includes versions org.apache.logging.log4j:log4j-core:2.3.1, org.apache.logging.log4j:log4j-core:2.12.2, org.apache.logging.log4j:log4j-core:2.15.0, and org.ops4j.pax.logging:pax-logging-log4j2:1.11.10,2.0.11

CVE-2017-5645: Deserialization of Untrusted Data

CVE-2017-5645 involves the deserialization of untrusted data in Apache Log4j 2.x versions before 2.8.2. When the TCP socket server or UDP socket server is used to receive serialized log events, a crafted binary payload can be sent, leading to arbitrary code execution when deserialized. This vulnerability allows attackers to inject malicious code into the system via carefully constructed log events. This type of attack underscores the importance of input validation and secure handling of data received from external sources. Organizations must ensure that they have implemented appropriate security measures to prevent such attacks.

• Vulnerability Details: This vulnerability affects Log4j 2.x versions before 2.8.2. A specially crafted binary payload can be sent when receiving serialized log events using the TCP or UDP socket server, leading to arbitrary code execution upon deserialization.
• Threat Assessment: Exploit Maturity is not defined, with an EPSS score of 94.0%.
• Suggested Fix: The recommended fix is to upgrade to org.apache.logging.log4j:log4j-core:2.8.2.

CVE-2021-45046: Incomplete Fix for CVE-2021-44228

CVE-2021-45046 represents a follow-up vulnerability to CVE-2021-44228. It highlights that the initial fix for CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in some non-default configurations. This means that even after applying the initial patch, systems remained vulnerable under specific configurations. Attackers with control over Thread Context Map (MDC) input data and when the logging configuration uses a non-default Pattern Layout could exploit this. The attack leverages JNDI Lookup patterns, leading to information leaks and potential remote or local code execution.

• Vulnerability Details: The fix for CVE-2021-44228 in Apache Log4j 2.15.0 was found to be incomplete. Attackers can exploit this with control over Thread Context Map (MDC) input data. The logging configuration must use a non-default Pattern Layout with a Context Lookup or Thread Context Map pattern.
• Threat Assessment: Exploit Maturity is rated as High, with an EPSS score of 94.3%.
• Suggested Fix: The recommended fix is to upgrade to patched versions org.apache.logging.log4j:log4j-core:2.3.1, org.apache.logging.log4j:log4j-core:2.12.2, org.apache.logging.log4j:log4j-core:2.16.0 or org.ops4j.pax.logging:pax-logging-log4j2:1.11.10,2.0.11

CVE-2021-44832: JDBC Appender Vulnerability

CVE-2021-44832 highlights a remote code execution (RCE) vulnerability when a JDBC Appender is used with a JNDI LDAP data source URI. This vulnerability affects Log4j2 versions 2.0-beta7 through 2.17.0 (excluding security fix releases 2.3.2 and 2.12.4). Attackers can exploit this if they control the target LDAP server. The core of this vulnerability is the ability to execute arbitrary code by manipulating the JDBC appender configuration. This emphasizes the critical need to validate and secure configurations, particularly those that involve external data sources. The impact of this vulnerability can be severe, potentially leading to unauthorized access, data breaches, and other security incidents.

• Vulnerability Details: Apache Log4j2 versions 2.0-beta7 through 2.17.0 are vulnerable when a configuration uses a JDBC Appender with a JNDI LDAP data source URI. An attacker must have control of the target LDAP server.
• Threat Assessment: Exploit Maturity is rated as High, with an EPSS score of 50.4%.
• Suggested Fix: Upgrade to org.apache.logging.log4j:log4j-core:2.3.2, org.apache.logging.log4j:log4j-core:2.12.4, or org.apache.logging.log4j:log4j-core:2.17.1

CVE-2021-45105: Denial of Service via Recursive Lookups

CVE-2021-45105 highlights a denial-of-service (DoS) vulnerability due to uncontrolled recursion from self-referential lookups in Apache Log4j2. Versions 2.0-alpha1 through 2.16.0 (excluding 2.12.3 and 2.3.1) are affected by this vulnerability. An attacker can cause a denial of service by controlling the Thread Context Map data and crafting a specific string to trigger uncontrolled recursion. This leads to the exhaustion of system resources, making the application unavailable. The key to mitigating this type of vulnerability is to restrict and validate user-supplied input, especially when it is used in configuration or logging statements.

• Vulnerability Details: Apache Log4j2 versions 2.0-alpha1 through 2.16.0 did not protect from uncontrolled recursion from self-referential lookups. This allows an attacker to cause a denial of service when a crafted string is interpreted.
• Threat Assessment: Exploit Maturity is rated as High, with an EPSS score of 65.7%.
• Suggested Fix: The recommended fix is to upgrade to org.apache.logging.log4j:log4j-core:2.3.1, org.apache.logging.log4j:log4j-core:2.12.3, or org.apache.logging.log4j:log4j-core:2.17.0 and org.ops4j.pax.logging:pax-logging-log4j2:1.11.10,2.0.11

CVE-2020-9488: Certificate Validation Issue in SMTP Appender

CVE-2020-9488 describes an improper validation of certificates with host mismatches in the Apache Log4j SMTP appender. This vulnerability could lead to a man-in-the-middle attack, where an attacker can intercept the SMTPS connection and potentially leak log messages sent through that appender. This is a crucial reminder of the importance of secure communication protocols and proper certificate validation. Attackers can exploit this flaw to intercept sensitive data transmitted through the SMTP appender.

• Vulnerability Details: Improper validation of certificates with host mismatch in the Apache Log4j SMTP appender. This could allow an SMTPS connection to be intercepted by a man-in-the-middle attack which could leak any log messages sent through that appender.
• Threat Assessment: Exploit Maturity is not defined, with an EPSS score of less than 1%.
• Suggested Fix: The fix is available in ch.qos.reload4j:reload4j:1.2.18.3

Conclusion

The identified vulnerabilities in log4j-core-2.6.1.jar highlight the critical importance of maintaining up-to-date software, performing regular security audits, and implementing robust security practices. From the critical RCE vulnerabilities (CVE-2021-44228, CVE-2017-5645, CVE-2021-45046) to the DoS and information-leaking issues (CVE-2021-45105, CVE-2021-44832, CVE-2020-9488), the potential impact on system security is substantial. By promptly addressing these vulnerabilities through the recommended fixes, organizations can significantly reduce their risk exposure and protect their systems from potential attacks. Staying informed about the latest security threats and best practices is essential for a proactive security posture.

For further reading and more in-depth information on Apache Log4j and its security, visit the official Apache Logging Services website: Apache Logging Services