CVE-2009-0544 in ARC2
Summary
by MITRE
Buffer overflow in the PyCrypto ARC2 module 2.0.1 allows remote attackers to cause a denial of service and possibly execute arbitrary code via a large ARC2 key length.
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Analysis
by VulDB Data Team • 05/11/2025
The vulnerability identified as CVE-2009-0544 represents a critical buffer overflow flaw within the PyCrypto library's ARC2 cryptographic module version 2.0.1. This issue resides in the implementation of the ARC2 encryption algorithm which is a symmetric key block cipher developed by Ronald Rivest. The vulnerability specifically manifests when the module processes cryptographic key lengths that exceed the allocated buffer space, creating a condition where memory corruption can occur during key handling operations. The PyCrypto library serves as a fundamental cryptographic toolkit for python applications, making this vulnerability particularly concerning for systems relying on secure communications and data protection mechanisms. The flaw affects the cryptographic processing pipeline where key material is validated and prepared for encryption operations, creating a potential entry point for malicious actors to manipulate the application's memory state.
The technical implementation of this buffer overflow stems from inadequate input validation within the ARC2 key processing routine. When a remote attacker provides an oversized key length parameter, the module fails to properly bounds-check the input against the allocated memory buffer. This creates a classic stack-based buffer overflow condition where the excess data overflows into adjacent memory locations, potentially corrupting critical program state information including return addresses, function pointers, and other control structures. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which occurs when data is copied into a stack buffer without proper size validation. The flaw is particularly dangerous because it can be triggered through normal cryptographic operations, meaning that legitimate users performing valid encryption tasks could inadvertently expose the system to exploitation if the key length parameter is manipulated or if the application is configured to accept user-provided key data.
From an operational perspective, this vulnerability creates multiple attack vectors that can lead to significant system compromise. The primary impact involves denial of service through application crashes and system instability, but the more severe implications involve potential code execution capabilities that could allow attackers to gain unauthorized access to system resources. The attack requires remote exploitation through network-based interactions with applications utilizing the vulnerable PyCrypto library, making it particularly dangerous for web applications, network services, and any system that handles cryptographic operations with external inputs. Attackers can leverage this vulnerability to execute arbitrary code with the privileges of the affected application, potentially leading to complete system compromise, data exfiltration, or establishment of persistent backdoors. The vulnerability also impacts the integrity of cryptographic operations, as corrupted memory could lead to incorrect encryption or decryption results, undermining the security assurances that cryptographic systems are designed to provide. This flaw directly relates to ATT&CK technique T1059.007 for command and script interpreter usage and T1203 for exploitation for privilege escalation.
Mitigation strategies for CVE-2009-0544 must address both immediate remediation and long-term architectural improvements. The most direct solution involves upgrading to a patched version of the PyCrypto library where buffer bounds checking has been properly implemented and key length validation has been strengthened. Organizations should also implement input sanitization measures at application layers that process cryptographic key data, ensuring that all key length parameters are validated against predefined maximum limits before being passed to cryptographic libraries. Network segmentation and access controls should be implemented to limit exposure of systems that utilize the vulnerable library, particularly in environments where untrusted inputs may be processed. Additionally, application developers should adopt defensive programming practices including stack canaries, address space layout randomization, and other exploit mitigation techniques. The vulnerability highlights the importance of regular security assessments and dependency management, as this flaw existed for several years without detection, emphasizing the need for continuous monitoring of cryptographic libraries and their security posture. Organizations should also consider migrating to more modern cryptographic libraries such as cryptography.py or other well-maintained alternatives that have demonstrated better security practices and more frequent updates to address emerging threats.