CVE-2022-43281 - Heap Overflow Vulnerability in wasm-interp v1..29: Detailed Analysis and Exploit Guide

A new vulnerability, CVE-2022-43281, has been discovered to affect wasm-interp v1..29. This post aims to provide an in-depth analysis of the vulnerability, its root cause, and exploit details, along with code snippets and references to original sources. Please note that exploiting this vulnerability may have serious consequences, so the information provided is intended for educational and research purposes only.

Overview

wasm-interp is a popular WebAssembly interpreter written in C++, part of the WABT: The WebAssembly Binary Toolkit project. The toolkit helps developers work effectively with the WebAssembly binary format, providing various utilities and tools.

The vulnerability (CVE-2022-43281) lies in the std::vector<wabt::Type, std::allocator<wabt::Type>>::size() function at the /bits/stl_vector.h file. This issue is caused by a heap overflow, which can be exploited by an attacker to execute arbitrary code.

Vulnerability Details

The vulnerable component is located in the std::vector class implementation, which is part of the C++ Standard Library. The issue occurs because the size() function doesn't correctly handle resizing the vector when it reaches its maximum capacity. This results in a buffer overflow, allowing data outside the buffer to be overwritten.

Here's the problematic code snippet from /bits/stl_vector.h

    template<typename _Tp, typename _Alloc>
      inline
      typename vector<_Tp, _Alloc>::size_type
      vector<_Tp, _Alloc>::
      size() const _GLIBCXX_NOEXCEPT
      { return size_type(this->_M_impl._M_finish - this->_M_impl._M_start); }

The size() function calculates the vector's size by subtracting the _M_start pointer from the _M_finish pointer. However, the _M_finish pointer isn't properly updated when the vector's capacity is exceeded, causing it to be larger than the actual allocated buffer. This results in a heap overflow.

Exploitation

To exploit the vulnerability, an attacker can craft a specially malformed WebAssembly binary and pass it to wasm-interp. This crafted input will cause an overflow, allowing the attacker to overwrite the memory and potentially execute arbitrary code.

There isn't a working exploit available currently, since the vulnerability hasn't been patched yet. However, researchers are working on a proof of concept (PoC) exploiting this vulnerability. Stay tuned for updates!

Mitigation

Currently, there is no official patch available to fix the vulnerability in wasm-interp. Until a patch is released by the developers, it's recommended to avoid using wasm-interp v1..29, and instead use an alternative WebAssembly interpreter without this vulnerability.

Conclusion

In conclusion, CVE-2022-43281 is a critical heap overflow vulnerability found in wasm-interp v1..29. Exploiting this issue can lead to arbitrary code execution. A patch is not available yet, so it is crucial to avoid using the vulnerable version of wasm-interp and switch to a safer alternative. Stay vigilant and follow security best practices to minimize the risk of exploitation.

References

1. WABT: The WebAssembly Binary Toolkit GitHub Repository
2. CVE-2022-43281 on NVD
3. C++ Reference for std::vector

Timeline

Published on: 10/28/2022 21:15:00 UTC
Last modified on: 11/01/2022 16:35:00 UTC