CVE-2018-16765 in WAVM
Summary
by MITRE
In WAVM through 2018-07-26, a crafted file sent to the WebAssembly Virtual Machine may cause a denial of service (application crash) or possibly have unspecified other impact because of an unspecified "heap-buffer-overflow" condition in FunctionValidationContext::else_.
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Analysis
by VulDB Data Team • 05/07/2023
The vulnerability identified as CVE-2018-16765 affects WAVM version 2018-07-26 and earlier, representing a critical heap-buffer-overflow condition within the WebAssembly Virtual Machine implementation. This flaw manifests during the validation process of WebAssembly modules when processing crafted input files, specifically within the FunctionValidationContext::else_ function. The heap-buffer-overflow condition occurs when the virtual machine attempts to access memory locations beyond the allocated buffer boundaries, creating a potential pathway for system instability and denial of service attacks. Such vulnerabilities fall under the CWE-121 category of Buffer Overflow, specifically manifesting as heap-based buffer overflows that can lead to application crashes and memory corruption.
The technical execution of this vulnerability involves the manipulation of WebAssembly bytecode structures during validation phases, where maliciously crafted module content triggers improper memory management within the FunctionValidationContext class. When the else_ validation method processes certain conditional constructs, it fails to properly bounds-check memory accesses, allowing attackers to write beyond allocated heap memory regions. This condition can result in application termination, memory corruption, or potentially more severe consequences depending on the execution environment and memory layout. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1499.004 for Network Denial of Service, as it can be exploited through crafted input delivery to disrupt service availability.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as heap buffer overflows can potentially enable more sophisticated attack vectors including code execution or privilege escalation depending on the system configuration. In environments where WAVM is used for sandboxed execution of untrusted WebAssembly modules, this vulnerability creates a significant risk for attackers seeking to compromise system stability or gain unauthorized access. The vulnerability affects any system running WAVM versions prior to the patch release, particularly impacting applications that process external WebAssembly content or serve as WebAssembly execution environments for user-submitted code. Organizations utilizing WebAssembly virtualization platforms must prioritize immediate patching to mitigate this heap-buffer-overflow condition that could be exploited to cause system instability or potentially more serious security consequences.
Mitigation strategies for CVE-2018-16765 should include immediate deployment of patched WAVM versions, implementation of input validation and sanitization for all WebAssembly module processing, and deployment of runtime monitoring to detect anomalous memory access patterns. Additional protective measures include restricting execution permissions for WebAssembly modules, implementing memory protection mechanisms such as stack canaries, and utilizing address space layout randomization to complicate exploitation attempts. Security teams should also consider implementing network segmentation and access controls to limit exposure of WAVM instances to untrusted inputs while maintaining comprehensive logging and monitoring capabilities to detect potential exploitation attempts. The vulnerability underscores the importance of rigorous input validation and memory safety practices in virtual machine implementations, particularly when handling untrusted code execution environments.