CVE-2015-3256 in PolicyKit
Summary
by MITRE
PolicyKit (aka polkit) before 0.113 allows local users to cause a denial of service (memory corruption and polkitd daemon crash) and possibly gain privileges via unspecified vectors, related to "javascript rule evaluation."
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Analysis
by VulDB Data Team • 06/25/2022
PolicyKit or polkit represents a critical access control framework that governs authorization for system-level operations in Linux and Unix-like operating systems. The vulnerability identified as CVE-2015-3256 affects versions prior to 0.113 and specifically targets the javascript rule evaluation mechanism within the polkit daemon. This flaw exists in the way the system processes javascript-based authorization rules, creating opportunities for malicious actors to exploit the underlying implementation. The vulnerability manifests through memory corruption issues that can lead to complete daemon crashes and potential privilege escalation, making it particularly dangerous in multi-user environments where administrative access controls are paramount.
The technical exploitation of this vulnerability occurs during javascript rule evaluation when malformed or specially crafted javascript code is processed by the polkitd daemon. This processing flaw allows attackers to manipulate memory structures in ways that were not anticipated during the original design phase. The vulnerability falls under CWE-121, which describes heap-based buffer overflow conditions, and potentially CWE-122, which covers buffer overflow vulnerabilities in heap memory. These memory corruption issues arise from inadequate input validation and bounds checking within the javascript evaluation engine that polkit employs to process authorization rules. The javascript engine used by polkit processes user-defined policies that can be loaded from various configuration files, creating multiple potential attack vectors.
The operational impact of CVE-2015-3256 extends beyond simple denial of service conditions to include potential privilege escalation capabilities that could allow local attackers to execute arbitrary code with elevated privileges. This vulnerability affects systems where polkit is actively used for authorization decisions, which includes most modern Linux distributions that implement desktop environments and system management tools. The daemon crash scenario creates immediate availability issues for system authorization services, while the privilege escalation component could enable attackers to gain administrative access to affected systems. This vulnerability is particularly concerning in enterprise environments where polkit is used to control access to system resources and administrative functions. The attack surface is broad as many system services and desktop applications rely on polkit for authorization decisions, making this vulnerability a significant threat to system integrity and security.
Mitigation strategies for CVE-2015-3256 focus primarily on upgrading to polkit version 0.113 or later, which contains patches addressing the javascript evaluation flaws. System administrators should also implement strict file permissions and access controls for polkit configuration files to prevent unauthorized modification of javascript rules. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the T1068 privilege escalation through local exploitation. Organizations should also consider implementing monitoring solutions that can detect unusual patterns in polkit daemon behavior or memory allocation patterns that might indicate exploitation attempts. Additionally, regular security assessments should verify that polkit configurations do not contain unnecessary or overly permissive javascript rules that could be exploited. The vulnerability demonstrates the importance of proper input validation and memory management in security-critical components, reinforcing the need for comprehensive security testing of authorization frameworks and their underlying scripting engines.