CVE-2019-7701 in Binaryen
Summary
by MITRE
A heap-based buffer over-read was discovered in wasm::SExpressionParser::skipWhitespace() in wasm-s-parser.cpp in Binaryen 1.38.22. A crafted wasm input can cause a segmentation fault, leading to denial-of-service, as demonstrated by wasm2js.
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Analysis
by VulDB Data Team • 07/09/2023
The vulnerability identified as CVE-2019-7701 represents a critical heap-based buffer over-read condition within the Binaryen webassembly toolchain version 1.38.22. This flaw specifically resides in the wasm::SExpressionParser::skipWhitespace() function located in the wasm-s-parser.cpp file, which forms a core component of the Binaryen compiler infrastructure used for processing webassembly files. The vulnerability manifests when processing malformed webassembly input files that contain crafted sequences designed to trigger the buffer over-read behavior.
The technical implementation of this vulnerability exploits the insufficient bounds checking within the skipWhitespace() function which processes whitespace characters in webassembly s-expression format parsing. When the parser encounters malformed input containing specially constructed byte sequences, it fails to properly validate buffer boundaries during memory access operations, leading to read operations that extend beyond allocated heap memory regions. This over-read condition occurs because the parser does not adequately verify the length of input data against available buffer space, allowing malicious input to cause the parser to access memory locations that do not belong to the intended data structure.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions to potentially enable more sophisticated attack vectors. When exploited through the wasm2js tool as demonstrated in the vulnerability report, the buffer over-read can cause segmentation faults that crash the processing application, effectively rendering the tool unusable for legitimate webassembly file conversion tasks. This denial-of-service condition affects developers and deployment environments that rely on Binaryen for webassembly compilation and transformation workflows, potentially disrupting continuous integration pipelines, development environments, and automated build systems that depend on these tools.
Security practitioners should recognize this vulnerability as aligning with CWE-125: "Out-of-bounds Read" and potentially related to CWE-787: "Out-of-bounds Write" through the broader category of memory safety issues in parsing libraries. The vulnerability also maps to ATT&CK technique T1059.007: "Command and Scripting Interpreter: JavaScript" as it affects tools that process webassembly files which may contain JavaScript components, and T1499.004: "Network Denial of Service: Resource Exhaustion" through the potential for resource exhaustion via repeated exploitation attempts. Organizations using Binaryen should implement immediate mitigation strategies including updating to patched versions, implementing input validation measures, and deploying sandboxed execution environments for webassembly processing to prevent exploitation of this heap-based buffer over-read condition that can compromise system availability and stability.