CVE-2022-1071 in mruby
Summary
by MITRE • 03/26/2022
User after free in mrb_vm_exec in GitHub repository mruby/mruby prior to 3.2.
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Analysis
by VulDB Data Team • 03/27/2022
The vulnerability identified as CVE-2022-1071 represents a critical user after free condition within the mruby interpreter's virtual machine execution engine. This flaw exists in the mrb_vm_exec function of the mruby repository and affects versions prior to 3.2, making it a significant security concern for systems that rely on this lightweight ruby implementation. The issue stems from improper memory management practices where user-controlled data can trigger memory deallocation followed by subsequent access to the freed memory location, creating potential exploitation vectors for remote attackers.
The technical nature of this vulnerability aligns with CWE-416, which specifically addresses the use of freed memory condition in software systems. When the mruby interpreter processes certain ruby code sequences, the virtual machine execution engine fails to properly validate memory references after deallocation occurs. This memory corruption vulnerability can manifest when the interpreter encounters specific bytecode patterns that lead to the freeing of memory segments while user-provided input or code continues to reference those locations. The flaw operates at the intersection of memory management and code execution, where the interpreter's virtual machine fails to maintain proper reference counting or memory state tracking mechanisms.
The operational impact of CVE-2022-1071 extends beyond simple memory corruption, as it can potentially enable arbitrary code execution within the context of the mruby interpreter. Attackers who can craft malicious ruby code or influence the input processed by the interpreter may exploit this vulnerability to execute arbitrary commands, escalate privileges, or cause denial of service conditions. The vulnerability is particularly concerning in environments where mruby serves as a scripting engine for web applications, embedded systems, or server-side processing where user input flows through the interpreter. This aligns with ATT&CK technique T1059.007 for script-based execution and T1133 for external remote services, as the vulnerability can be exploited through crafted ruby code execution.
Mitigation strategies for CVE-2022-1071 primarily involve upgrading to mruby version 3.2 or later, which contains the necessary patches to address the memory management issues within the mrb_vm_exec function. Organizations should also implement input validation and sanitization measures to reduce the attack surface, particularly when processing untrusted ruby code or user-generated content through the interpreter. Additionally, deployment of runtime protections such as address space layout randomization and stack canaries can provide additional defense-in-depth measures. The vulnerability demonstrates the critical importance of proper memory management in interpreted languages and highlights the need for comprehensive testing of memory safety mechanisms in scripting engines that handle user input. Security teams should conduct thorough vulnerability assessments of systems using affected mruby versions and implement monitoring for potential exploitation attempts through anomalous code execution patterns or memory access violations.