CVE-2021-3100 in Linux
Summary
by MITRE • 04/20/2022
The Apache Log4j hotpatch package before log4j-cve-2021-44228-hotpatch-1.1-12 didn’t mimic the permissions of the JVM being patched, allowing it to escalate privileges.
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Analysis
by VulDB Data Team • 04/27/2022
The vulnerability identified as CVE-2021-3100 affects the Apache Log4j hotpatch package, specifically versions prior to log4j-cve-2021-44228-hotpatch-1.1-12. This issue represents a privilege escalation vulnerability that arises from improper permission handling during the patching process of the widely used Java logging library. The flaw occurs when the hotpatch package fails to correctly replicate the permissions of the target Java Virtual Machine environment, creating a security gap that adversaries can exploit to gain elevated system privileges. This vulnerability is particularly concerning because it directly impacts the security posture of systems running vulnerable Log4j versions, especially in environments where the hotpatch mechanism is deployed as a temporary mitigation strategy before full patching can be implemented.
The technical root cause of this vulnerability stems from the hotpatch implementation's failure to maintain proper access controls and permission boundaries when modifying the JVM runtime environment. When the hotpatch package executes, it should preserve the original permission model of the target Java process but instead creates a mismatch that allows unauthorized privilege elevation. This permission mismatch creates an attack surface where malicious actors can manipulate the patched JVM to execute code with higher privileges than intended. The vulnerability specifically relates to the improper handling of file permissions and process access controls during the hotpatch installation phase, which can be exploited through various attack vectors including malicious code injection or privilege escalation techniques.
The operational impact of CVE-2021-3100 extends beyond the immediate privilege escalation capabilities, as it undermines the fundamental security assumptions of systems relying on the Log4j hotpatch mechanism. Organizations that deploy hotpatches as interim solutions before full patching may unknowingly create persistent security vulnerabilities that adversaries can leverage to establish persistent access to critical systems. The vulnerability affects enterprise environments where Log4j is extensively used for application logging, making it a significant concern for organizations with large Java-based infrastructures. Attackers can exploit this weakness to move laterally within networks, escalate privileges to system-level access, and potentially gain control over entire server environments. The impact is particularly severe given that Log4j is a core component in many enterprise applications, making the privilege escalation opportunity widespread across affected systems.
Mitigation strategies for CVE-2021-3100 require immediate action to upgrade to the patched version of the hotpatch package, specifically log4j-cve-2021-44228-hotpatch-1.1-12 or later. System administrators should conduct comprehensive inventory assessments to identify all systems running vulnerable hotpatch versions and implement immediate upgrades. Additionally, organizations should review and audit their permission models for Java processes and hotpatch installations to ensure proper access controls are maintained. The vulnerability aligns with CWE-276, which addresses improper permissions and access control issues, and can be categorized under ATT&CK techniques related to privilege escalation and persistence mechanisms. Organizations should also implement monitoring solutions to detect unauthorized privilege changes and ensure that any hotpatch deployment follows strict security protocols to maintain proper file and process permissions throughout the patching lifecycle.