CVE-2020-25489 in PyMiniRacer
Summary
by MITRE
A heap overflow in Sqreen PyMiniRacer (aka Python Mini Racer) before 0.3.0 allows remote attackers to potentially exploit heap corruption.
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Analysis
by VulDB Data Team • 09/18/2020
The heap overflow vulnerability in Sqreen PyMiniRacer represents a critical security flaw that affects the Python Mini Racer library version 0.2.0 and earlier. This vulnerability stems from improper memory management during JavaScript execution within Python environments, creating a condition where malicious input can trigger buffer overflows in heap memory allocation. The flaw specifically impacts applications that utilize the PyMiniRacer library to execute JavaScript code, making it particularly dangerous in web applications and server-side environments where JavaScript execution is common. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though it manifests as a heap overflow due to the memory allocation patterns used by the library. Attackers can potentially leverage this vulnerability to execute arbitrary code, cause application crashes, or perform denial of service attacks against systems that rely on this JavaScript engine integration.
The technical exploitation of this heap overflow occurs when the PyMiniRacer library processes malformed JavaScript input that exceeds allocated buffer boundaries in the heap memory space. The vulnerability arises from insufficient bounds checking during JavaScript string processing and memory allocation operations. When a malicious payload is passed to the JavaScript engine through PyMiniRacer, the library fails to properly validate input sizes before allocating heap memory, leading to memory corruption that can be exploited through various attack vectors including memory spraying techniques. This type of vulnerability falls under the ATT&CK framework's technique T1059.007 for JavaScript execution, where adversaries manipulate the execution environment to achieve unauthorized code execution. The heap corruption can result in unpredictable behavior including memory leaks, application crashes, or more severe exploitation opportunities that could lead to complete system compromise.
The operational impact of CVE-2020-25489 extends beyond simple application instability to potentially enable full system compromise in vulnerable environments. Systems that integrate PyMiniRacer for server-side JavaScript execution, such as web applications, API gateways, or microservices, become vulnerable to remote code execution attacks. The vulnerability is particularly concerning because it affects the underlying JavaScript engine integration rather than just the Python wrapper, meaning that any application using PyMiniRacer to execute untrusted JavaScript input is at risk. This includes content management systems, web frameworks, and any application that relies on JavaScript execution for dynamic content processing. The vulnerability's remote exploitation capability means that attackers can trigger the heap overflow through network-based inputs without requiring local access to the system, making it a high-severity threat for internet-facing applications.
Mitigation strategies for this heap overflow vulnerability require immediate patching of the PyMiniRacer library to version 0.3.0 or later, which includes proper bounds checking and memory allocation safeguards. Organizations should implement input validation measures at multiple layers including API gateways, web application firewalls, and application-level sanitization to reduce the attack surface. Additionally, deploying runtime protections such as address space layout randomization and stack canaries can help mitigate exploitation attempts. The remediation process should include comprehensive testing to ensure that the patched version functions correctly with existing applications while maintaining security. Security monitoring should be enhanced to detect unusual JavaScript execution patterns that might indicate exploitation attempts, and regular vulnerability scanning should be implemented to identify other potentially vulnerable components in the application stack. Organizations should also consider implementing principle of least privilege access controls and network segmentation to limit the potential impact of successful exploitation attempts.