CVE-2014-2209 in HipHop Virtual Machine
Summary
by MITRE
Facebook HipHop Virtual Machine (HHVM) before 3.1.0 does not drop supplemental group memberships within hphp/util/capability.cpp and hphp/util/light-process.cpp, which allows remote attackers to bypass intended access restrictions by leveraging group permissions for a file or directory.
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Analysis
by VulDB Data Team • 04/10/2022
The vulnerability identified as CVE-2014-2209 affects Facebook's HipHop Virtual Machine HHVM version 3.1.0 and earlier, representing a critical security flaw in privilege management and access control mechanisms. This issue resides within the core capability handling components of HHVM, specifically in the files hphp/util/capability.cpp and hphp/util/light-process.cpp, which are responsible for managing process capabilities and group memberships during execution. The flaw manifests when HHVM fails to properly drop supplemental group memberships during process initialization, creating a persistent security risk that can be exploited by remote attackers to gain unauthorized access to restricted resources.
The technical nature of this vulnerability stems from improper privilege separation within the virtual machine's execution environment. When HHVM processes execute, they should drop all unnecessary group memberships to minimize the attack surface and prevent privilege escalation. However, the implementation in affected versions fails to properly clear supplemental group IDs, allowing processes to maintain elevated permissions from their parent processes. This behavior creates a direct pathway for attackers to leverage existing group permissions associated with files or directories, effectively bypassing intended access controls that should restrict unauthorized access to sensitive resources.
From an operational impact perspective, this vulnerability represents a significant risk to systems running HHVM, particularly those hosting web applications that process user input or access sensitive data. Attackers can exploit this weakness to gain access to files or directories that should be restricted to specific user groups or permissions. The vulnerability is particularly dangerous because it operates at the process level within the virtual machine, meaning that any application running within HHVM could be compromised. This affects not only the immediate application but potentially the entire system, as the compromised process retains access to resources that should be restricted based on group membership.
The security implications align with CWE-276, which describes improper file permissions, and relates to the broader category of privilege escalation vulnerabilities. This flaw can be exploited through various attack vectors including web-based applications that utilize HHVM, potentially allowing attackers to read restricted files, execute arbitrary code with elevated privileges, or gain access to sensitive system resources. The ATT&CK framework categorizes this as a privilege escalation technique, specifically under the T1068 - Exploitation for Privilege Escalation tactic, where attackers leverage system weaknesses to gain higher-level permissions.
Mitigation strategies for this vulnerability require immediate patching of HHVM installations to version 3.1.0 or later, where the supplemental group membership dropping functionality has been properly implemented. System administrators should also implement additional security controls including regular privilege reviews, monitoring for unauthorized process execution with elevated group memberships, and ensuring proper file permissions are enforced at the filesystem level. Organizations should conduct thorough security assessments to identify any processes running with unnecessary group memberships and implement principle of least privilege configurations to minimize the potential impact of such vulnerabilities. Additionally, network segmentation and access controls should be reviewed to limit the blast radius of any successful exploitation attempts.