CVE-2012-1502 in PyPAM
Summary
by MITRE
Double free vulnerability in the PyPAM_conv in PAMmodule.c in PyPam 0.5.0 and earlier allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a NULL byte in a password string.
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Analysis
by VulDB Data Team • 01/02/2025
The vulnerability identified as CVE-2012-1502 represents a critical double free condition within the PyPAM_conv function of the PAMmodule.c file in PyPam versions 0.5.0 and earlier. This flaw resides in the authentication module handling mechanism that processes password inputs through the Pluggable Authentication Modules framework. The vulnerability manifests when a remote attacker submits a password string containing a NULL byte, which triggers improper memory management within the Python PAM binding implementation. The double free occurs because the vulnerable code path attempts to free the same memory location twice during the processing of the malformed input, creating a scenario where memory corruption can occur.
This memory corruption vulnerability directly maps to CWE-415, which specifically addresses double free conditions in memory management operations. The flaw operates at the intersection of software security and authentication systems, where the PyPAM library serves as a bridge between Python applications and the underlying PAM authentication infrastructure. When the NULL byte is processed, the memory allocation functions within the PAM module fail to properly track memory references, leading to the second free operation attempting to release already-deallocated memory blocks. This creates a predictable pattern of memory corruption that can be exploited to manipulate the program's execution flow.
The operational impact of this vulnerability extends beyond simple denial of service, as the memory corruption potential opens avenues for arbitrary code execution. Attackers can leverage this condition to cause application crashes or potentially gain remote code execution privileges depending on the system configuration and memory layout. The vulnerability affects systems that rely on PyPAM for authentication processes, particularly those running vulnerable versions of the library. From an adversarial perspective, this represents a sophisticated attack vector that can be executed remotely without requiring authentication, making it particularly dangerous for systems that expose PAM-based authentication interfaces.
The attack surface for CVE-2012-1502 encompasses any application or service that utilizes PyPAM for authentication and accepts user input through password fields. The vulnerability aligns with ATT&CK technique T1548.003, which covers abuse of authentication tokens, particularly in contexts where authentication modules are improperly handled. Systems running vulnerable PyPAM versions in web applications, network services, or authentication daemons become susceptible to exploitation. The NULL byte injection attack vector requires minimal privileges to execute, as the vulnerability exists within the input processing layer rather than requiring elevated system access.
Mitigation strategies for this vulnerability involve immediate version updates to PyPAM 0.5.1 or later, which contain the necessary patches to address the double free condition. System administrators should conduct comprehensive vulnerability assessments to identify all systems utilizing vulnerable PyPAM versions and implement patch management procedures to ensure timely remediation. Additional protective measures include input validation mechanisms that sanitize password strings before processing, particularly focusing on null byte detection and removal. The implementation of memory protection features such as stack canaries, address space layout randomization, and heap metadata protection can provide additional defense-in-depth layers. Organizations should also consider implementing monitoring solutions to detect anomalous authentication patterns that might indicate exploitation attempts, while maintaining regular security audits to identify similar memory management flaws in other authentication modules.