CVE-2019-7702 in Binaryen
Summary
by MITRE
A NULL pointer dereference was discovered in wasm::SExpressionWasmBuilder::parseExpression 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 wasm-as.
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Analysis
by VulDB Data Team • 07/09/2023
The vulnerability identified as CVE-2019-7702 represents a critical null pointer dereference flaw within the Binaryen webassembly toolchain version 1.38.22. This issue specifically affects the wasm::SExpressionWasmBuilder::parseExpression function located in the wasm-s-parser.cpp file, which serves as a crucial component for parsing webassembly text format files. The flaw arises when processing malformed webassembly input files that contain specially crafted sequences designed to trigger the null pointer dereference condition during the parsing phase of the wasm-as tool.
The technical implementation of this vulnerability stems from inadequate input validation within the parsing logic of the webassembly text format parser. When the SExpressionWasmBuilder attempts to process malformed webassembly expressions, it fails to properly handle cases where pointers remain uninitialized or are explicitly set to null values during the parsing workflow. This failure occurs specifically during the expression parsing phase where the code assumes certain pointer values will be properly initialized, but malicious input can bypass these initialization checks. The vulnerability is classified under CWE-476 as a null pointer dereference, which represents a fundamental programming error where the application attempts to access memory through a null pointer reference.
The operational impact of this vulnerability manifests as a denial-of-service condition that can be easily triggered by any user capable of providing crafted webassembly input files to the wasm-as tool. When exploited, the vulnerability results in a segmentation fault that terminates the application process, effectively rendering the webassembly compilation tool unusable for legitimate users. This type of vulnerability is particularly dangerous in automated build environments or continuous integration systems where wasm-as is invoked programmatically, as it can cause complete build failures and system outages. The attack vector is relatively simple and does not require advanced privileges or complex exploitation techniques, making it accessible to a wide range of threat actors.
From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1499.004 for network denial-of-service, as it specifically targets the availability of webassembly compilation tools. The vulnerability demonstrates characteristics of a remote code execution vector in contexts where untrusted webassembly input is processed, though the immediate impact is limited to denial-of-service. Organizations utilizing Binaryen for webassembly processing should consider this vulnerability as part of their broader security posture assessment, particularly in environments where webassembly files are compiled from untrusted sources. The vulnerability serves as a reminder of the critical importance of input validation and proper error handling in security-sensitive parsing components.
The recommended mitigation strategy involves upgrading to Binaryen version 1.38.23 or later, where the null pointer dereference has been addressed through proper input validation and pointer initialization checks. Additionally, organizations should implement strict input validation procedures for any webassembly files processed through the toolchain, including sandboxing the wasm-as tool execution environment to limit potential impact. System administrators should also consider implementing monitoring and alerting for segmentation fault occurrences in webassembly compilation processes, as these incidents may indicate attempted exploitation of similar vulnerabilities. The fix demonstrates the importance of comprehensive testing for edge cases in parsing components and highlights the need for robust defensive programming practices in security-critical software components.