CVE-2008-1887 in Python
Summary
by MITRE
Python 2.5.2 and earlier allows context-dependent attackers to execute arbitrary code via multiple vectors that cause a negative size value to be provided to the PyString_FromStringAndSize function, which allocates less memory than expected when assert() is disabled and triggers a buffer overflow.
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Analysis
by VulDB Data Team • 08/09/2019
The vulnerability identified as CVE-2008-1887 represents a critical buffer overflow flaw in Python versions 2.5.2 and earlier that stems from improper handling of string allocation parameters. This issue occurs when the PyString_FromStringAndSize function receives negative size values, creating a scenario where memory allocation behaves unexpectedly. The flaw specifically manifests when assert() checks are disabled during compilation, allowing malicious input to bypass runtime validation mechanisms that would normally prevent such dangerous memory operations.
The technical root cause of this vulnerability lies in the fundamental memory management approach within Python's string handling functions. When a negative size parameter is passed to PyString_FromStringAndSize, the function attempts to allocate memory based on this invalid value, resulting in insufficient memory allocation. This creates a buffer overflow condition where subsequent operations can overwrite adjacent memory locations, potentially allowing attackers to execute arbitrary code. The vulnerability's context-dependent nature means that exploitation requires specific conditions where the application processes user-supplied data that can influence the string size parameter.
From an operational perspective, this vulnerability poses significant risks to systems running affected Python versions, particularly those that process untrusted input through string operations. Attackers can craft malicious inputs that, when processed by Python applications, trigger the buffer overflow condition and potentially gain code execution privileges. The impact extends beyond simple code execution to potential system compromise, data corruption, and denial of service conditions. The vulnerability's exploitation becomes more likely in environments where Python applications handle external data sources such as network requests, file processing, or user input without proper validation.
The security implications of CVE-2008-1887 align with CWE-121, which describes heap-based buffer overflow conditions, and can be mapped to ATT&CK technique T1059.007 for execution through Python scripts. Organizations running vulnerable Python installations face heightened risk of compromise, particularly in web applications, network services, and any system where Python code processes external data. The vulnerability demonstrates how seemingly benign memory allocation functions can become attack vectors when proper input validation and parameter checking are absent.
Mitigation strategies for this vulnerability include immediate upgrade to Python versions 2.5.3 or later where the issue has been resolved through proper parameter validation and memory allocation checks. System administrators should implement comprehensive input validation measures, particularly for string operations that could be influenced by external data. Additionally, deploying runtime protections such as address space layout randomization and stack canaries can help reduce exploitability. Organizations should also conduct thorough code reviews to identify other potential buffer overflow conditions in their Python applications and ensure that assert() checks are properly configured in production environments to prevent similar issues from occurring.