CVE-2026-38973 in mrubyc
Summary
by MITRE • 07/06/2026
mrubyc through release3.4.1 was found to contain an out-of-bounds read in builtin missing-method lookup inside mrbc_find_method().
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Analysis
by VulDB Data Team • 07/07/2026
The vulnerability identified in mrubyc through release 3.4.1 represents a critical out-of-bounds read condition that occurs during the method lookup process within the mrbc_find_method() function. This flaw manifests when the system attempts to resolve missing methods during bytecode compilation, creating a scenario where memory access exceeds valid boundaries. The issue stems from inadequate bounds checking in the method resolution mechanism that governs how the interpreter handles undefined method references during compilation phases.
This vulnerability falls under the CWE-125 Out-of-Bounds Read classification, which specifically addresses situations where programs read memory locations beyond the intended buffer or array boundaries. The flaw operates at the intersection of software security and runtime behavior, where the mrubyc compiler fails to properly validate method resolution parameters before accessing internal data structures. When a missing method lookup occurs, the system attempts to traverse method tables or symbol dictionaries without proper boundary validation, leading to unauthorized memory access patterns.
The operational impact of this vulnerability extends beyond simple memory corruption, as it creates potential attack vectors for privilege escalation and code execution. An attacker could craft malicious input that triggers the out-of-bounds read condition during compilation, potentially allowing for information disclosure, denial of service, or more severe exploitation depending on the execution environment. The vulnerability is particularly concerning in environments where mrubyc is used to compile untrusted code or where automated compilation processes handle external inputs.
From an ATT&CK framework perspective, this vulnerability maps to technique T1059.007 Command and Scripting Interpreter: Python, as it affects the underlying compilation infrastructure that supports interpreted language execution. The flaw could enable adversaries to perform code injection attacks during the compilation phase of mruby applications, particularly in scenarios involving automated build processes or dynamic code generation. Security professionals should consider this vulnerability when assessing runtime environments where mrubyc is deployed.
Mitigation strategies for this vulnerability include immediate upgrade to patched versions of mrubyc beyond release 3.4.1, implementation of input validation measures during bytecode compilation, and deployment of memory safety monitoring tools. Additionally, organizations should implement strict code review processes for any custom modifications to the method lookup functionality and consider runtime application security protection measures that can detect and prevent out-of-bounds memory access patterns. The vulnerability highlights the importance of robust bounds checking in interpreter implementations and demonstrates how seemingly minor flaws in method resolution can create significant security risks across compiled environments.