Source: cna@vuldb.com
A security vulnerability has been detected in WebAssembly wabt up to 1.0.39. This issue affects the function wabt::Decompiler::VarName of the file /src/repro/wabt/bin/wasm-decompile of the component wasm-decompile. Such manipulation leads to out-of-bounds read. Local access is required to approach this attack. The exploit has been disclosed publicly and may be used. Unfortunately, the project has no active maintainer at the moment. In a reply to the issue report somebody recommended to the researcher to provide a PR himself.
WebAssembly (Wasm) wabt up to version 1.0.39 is vulnerable to an out-of-bounds read vulnerability, allowing for potential information disclosure and system compromise. The flaw resides in the wabt::Decompiler::VarName function within the wasm-decompile component, and a publicly disclosed exploit exists. Due to the lack of an active maintainer, patching this critical vulnerability is currently challenging, increasing the risk of exploitation.
Step 1: Payload Preparation: The attacker crafts a malicious WebAssembly (.wasm) file. This file is designed to exploit the vulnerability in wabt::Decompiler::VarName.
Step 2: Triggering Decompilation: The attacker provides the malicious .wasm file to a system that uses wasm-decompile from wabt (version <= 1.0.39). This could be through a local file upload, a network service that processes .wasm files, or any other mechanism that invokes the decompiler.
Step 3: Vulnerability Execution: The wasm-decompile tool attempts to decompile the malicious .wasm file. During the decompilation process, the wabt::Decompiler::VarName function is called.
Step 4: Out-of-Bounds Read: Due to the crafted .wasm file, the VarName function attempts to access memory outside the allocated bounds. This read operation retrieves data from an unintended memory location.
Step 5: Information Disclosure (or potential for further exploitation): The data read from the out-of-bounds location is either displayed to the attacker (information disclosure) or used in a way that allows the attacker to further control the system. The specific impact depends on the nature of the data read and how it is used by the application.
The vulnerability stems from an out-of-bounds read within the wabt::Decompiler::VarName function in wasm-decompile. The root cause is likely an improper bounds check or calculation when accessing memory associated with variable names during the decompilation process. Specifically, the code fails to validate the index used to access a data structure (e.g., an array or buffer) containing variable name information. This allows an attacker to provide a crafted WebAssembly file that, when decompiled, triggers an access outside the allocated memory region. This leads to the disclosure of sensitive information or, in more severe cases, could be leveraged to overwrite critical data, potentially leading to arbitrary code execution if the attacker can control the contents of the memory read.
While no specific APTs are directly linked to this vulnerability at this time, the public availability of the exploit makes it attractive to a wide range of attackers, including those seeking to gain initial access or escalate privileges. This vulnerability could be leveraged by any actor with the ability to provide a .wasm file to a vulnerable system. Not currently listed on CISA KEV, but given the public exploit and lack of patching, it is a high-priority target.
Monitor file system activity for the execution of wasm-decompile or related binaries, especially when handling untrusted .wasm files.
Analyze network traffic for the transfer of .wasm files, particularly if the source is external or untrusted.
Implement file integrity monitoring to detect modifications to wasm-decompile and related files.
Examine system logs for errors or crashes related to wasm-decompile or other components of the wabt library, especially those indicating memory access violations.
Use a static analysis tool to scan .wasm files for suspicious patterns or characteristics that might indicate an attempt to exploit the vulnerability.
Monitor for unusual memory access patterns or unexpected behavior during the decompilation process.
Patching is the primary remediation. Since there is no active maintainer, the best course of action is to identify a fork or alternative implementation of wabt that has addressed the vulnerability and integrate it into the affected systems. This may involve a significant effort.
Input Validation: If possible, implement robust input validation to filter or sanitize .wasm files before they are processed by wasm-decompile. This could involve checking file size, structure, and content to prevent malicious payloads.
Isolate the Decompilation Process: Run the wasm-decompile tool in a sandboxed environment or container to limit the potential impact of a successful exploit. This can restrict the attacker's ability to access sensitive system resources.
Disable or Restrict Usage: If the functionality provided by wasm-decompile is not essential, consider disabling it or restricting its use to trusted users or systems.
Monitor for Exploitation Attempts: Implement intrusion detection and prevention systems (IDS/IPS) to monitor for and block attempts to exploit the vulnerability. This includes monitoring for suspicious network traffic, file access patterns, and system behavior.
Regular Security Audits: Conduct regular security audits and penetration testing to identify and address vulnerabilities in the system.