CVE-2013-7459 in PyCrypto
Summary
by MITRE
Heap-based buffer overflow in the ALGnew function in block_templace.c in Python Cryptography Toolkit (aka pycrypto) allows remote attackers to execute arbitrary code as demonstrated by a crafted iv parameter to cryptmsg.py.
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Analysis
by VulDB Data Team • 08/14/2020
The vulnerability identified as CVE-2013-7459 represents a critical heap-based buffer overflow within the Python Cryptography Toolkit, specifically in the ALGnew function located in block_templace.c. This flaw exists in the cryptographic library's handling of initialization vectors during message encryption operations, creating a potential remote code execution vector that can be exploited by attackers positioned outside the local network. The vulnerability stems from insufficient input validation and memory management within the cryptographic processing pipeline, where the ALGnew function fails to properly bounds-check the iv parameter before processing it in memory.
The technical implementation of this vulnerability occurs when a maliciously crafted initialization vector parameter is passed to the cryptmsg.py script through the affected cryptographic toolkit. The ALGnew function in block_templace.c does not adequately validate the length or content of the initialization vector input, allowing an attacker to overflow heap-allocated memory buffers. This heap overflow can be carefully constructed to overwrite adjacent memory locations including return addresses or function pointers, enabling arbitrary code execution with the privileges of the affected application process. The vulnerability is particularly dangerous because it operates at the cryptographic layer where sensitive operations are performed, making it an attractive target for attackers seeking to compromise encrypted communications or gain unauthorized system access.
Operationally, this vulnerability poses significant risks to systems utilizing the Python Cryptography Toolkit for secure communications, data encryption, or cryptographic operations. Attackers can exploit this flaw remotely by crafting malicious initialization vectors that trigger the buffer overflow during normal cryptographic processing. The impact extends beyond simple code execution to potential data breaches, system compromise, and unauthorized access to encrypted data streams. Systems running vulnerable versions of pycrypto are at risk when they process untrusted input through cryptographic functions, particularly in network services that handle encrypted message processing or key management operations. The vulnerability's remote exploitability means that attackers do not need physical access to the target system, making it particularly dangerous in networked environments where cryptographic libraries are widely deployed.
Mitigation strategies for CVE-2013-7459 include immediate upgrading to patched versions of the Python Cryptography Toolkit, as the vulnerability has been addressed through proper bounds checking and memory management improvements in subsequent releases. Organizations should also implement network segmentation and access controls to limit exposure of systems using vulnerable cryptographic libraries, while monitoring for suspicious network traffic patterns that might indicate exploitation attempts. Input validation should be strengthened at all levels where cryptographic parameters are processed, and security teams should consider implementing runtime protections such as address space layout randomization and stack canaries to make exploitation more difficult. This vulnerability aligns with CWE-121, heap-based buffer overflow, and maps to attack techniques in the MITRE ATT&CK framework under privilege escalation and code execution tactics, emphasizing the need for comprehensive security remediation across all cryptographic implementations.