CVE-2020-18378 in Binaryen
Summary
by MITRE • 08/22/2023
A NULL pointer dereference was discovered in SExpressionWasmBuilder::makeBlock in wasm/wasm-s-parser.c in Binaryen 1.38.26. 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 • 10/04/2024
The vulnerability CVE-2020-18378 represents a critical null pointer dereference flaw within the Binaryen web assembly toolchain version 1.38.26. This issue resides in the SExpressionWasmBuilder::makeBlock function located in the wasm/wasm-s-parser.c file, which serves as a crucial component for parsing s-expression formatted web assembly files. The flaw manifests when processing malformed web assembly input, specifically crafted to trigger the null pointer dereference condition during the parsing phase of the wasm-as tool. This particular vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is a well-documented weakness in software systems where a pointer that is expected to point to a valid memory location is instead NULL, leading to program termination.
The technical exploitation of this vulnerability occurs when an attacker provides a specially crafted web assembly file that contains malformed s-expression syntax. During the parsing process, the makeBlock function attempts to dereference a pointer that has not been properly initialized or validated, resulting in an immediate segmentation fault. This segmentation fault causes the wasm-as tool to crash and terminate unexpectedly, effectively rendering the tool unusable for legitimate web assembly compilation tasks. The vulnerability is particularly concerning because it can be triggered through normal input processing without requiring any special privileges or complex attack vectors, making it accessible to potential adversaries who wish to disrupt web assembly toolchain operations.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions, as it can significantly disrupt development workflows and automated build systems that rely on Binaryen tools for web assembly compilation. When the wasm-as tool crashes due to this null pointer dereference, developers face interruptions in their development cycles, and continuous integration pipelines may fail unexpectedly. The vulnerability affects any system that processes web assembly files through the affected Binaryen version, including web assembly compilers, development environments, and deployment systems that utilize this toolchain. From an attacker perspective, this vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service, as it can be leveraged to disrupt services that depend on web assembly compilation capabilities.
Mitigation strategies for CVE-2020-18378 should prioritize immediate patching of the Binaryen toolchain to version 1.38.27 or later, which contains the necessary fixes for the null pointer dereference issue. Organizations should also implement input validation measures for web assembly files processed through the toolchain, including sanitization of s-expression inputs and runtime monitoring for abnormal termination patterns. Security teams should consider implementing sandboxing mechanisms around web assembly compilation processes to prevent complete system disruption should the vulnerability be exploited. Additionally, regular vulnerability assessments of web assembly toolchains and development environments should be conducted to identify similar issues in other components of the software stack. The fix implemented in the patched version addresses the root cause by ensuring proper pointer validation and initialization before dereferencing operations, thereby preventing the segmentation fault condition that previously led to denial-of-service scenarios.