CVE-2015-3255 in PolicyKit
Summary
by MITRE
The polkit_backend_action_pool_init function in polkitbackend/polkitbackendactionpool.c in PolicyKit (aka polkit) before 0.113 might allow local users to gain privileges via duplicate action IDs in action descriptions.
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Analysis
by VulDB Data Team • 06/25/2022
The vulnerability identified as CVE-2015-3255 affects PolicyKit, a system-level authorization framework that controls user permissions for system-wide operations in Unix-like operating systems. This flaw exists in the polkit_backend_action_pool_init function within the polkitbackendactionpool.c source file, specifically impacting versions prior to 0.113. The vulnerability stems from inadequate validation of action IDs during the initialization of the action pool, creating a scenario where duplicate identifiers can be processed without proper sanitization.
The technical implementation of this vulnerability exploits the lack of proper duplicate detection mechanisms within the PolicyKit action pool initialization process. When action descriptions are loaded, the system fails to verify that each action ID is unique within the pool context. This oversight allows malicious actors to craft action descriptions containing duplicate identifiers, which can then be processed by the system in unexpected ways. The flaw operates at the core of PolicyKit's authorization mechanism, where action IDs serve as critical identifiers for determining user permissions and access controls.
From an operational perspective, this vulnerability presents a significant privilege escalation risk for local users who can manipulate action descriptions to gain elevated system privileges. The impact extends beyond simple local privilege escalation as it can potentially allow attackers to bypass security controls that rely on specific action IDs for access decisions. Attackers could leverage this vulnerability to modify or manipulate authorization rules, effectively undermining the entire PolicyKit security model and potentially enabling unauthorized system modifications or data access. The vulnerability aligns with CWE-1004 which addresses insecure default settings and improper handling of duplicate identifiers in security-critical systems.
The exploitation of CVE-2015-3255 typically involves crafting malicious action description files that contain duplicate action IDs, which when processed by the vulnerable PolicyKit version, can result in unexpected behavior within the authorization subsystem. This attack vector falls under the ATT&CK technique T1068 which covers the use of privilege escalation techniques through local system manipulation. The vulnerability demonstrates a classic case of inadequate input validation where the system fails to properly sanitize or validate identifiers that are critical to security operations.
Mitigation strategies for this vulnerability primarily focus on immediate patching of PolicyKit to version 0.113 or later, which includes proper duplicate ID detection and handling mechanisms. System administrators should also implement strict file permissions on PolicyKit action description files to prevent unauthorized modifications. Additional protective measures include monitoring for unusual action pool initialization patterns and implementing regular security audits of authorization configurations. The fix addresses the underlying issue by introducing proper validation checks that ensure action ID uniqueness before processing, thereby preventing the exploitation scenario that leads to privilege escalation. Organizations should also consider implementing principle of least privilege configurations and regularly review their PolicyKit policies to minimize potential impact from similar vulnerabilities in the future.