CVE-2017-9527 in mruby
Summary
by MITRE
The mark_context_stack function in gc.c in mruby through 1.2.0 allows attackers to cause a denial of service (heap-based use-after-free and application crash) or possibly have unspecified other impact via a crafted .rb file.
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Analysis
by VulDB Data Team • 12/08/2022
The vulnerability identified as CVE-2017-9527 resides within the mruby interpreter's garbage collection mechanism, specifically in the mark_context_stack function located in gc.c. This flaw affects mruby versions through 1.2.0 and represents a critical heap-based use-after-free vulnerability that can be exploited through maliciously crafted ruby script files. The issue stems from improper memory management during the garbage collection process where the application fails to properly track and validate object references, creating opportunities for attackers to manipulate memory access patterns.
The technical exploitation of this vulnerability occurs when an attacker crafts a specific .rb file that triggers the mark_context_stack function with malformed input data. During garbage collection, the function attempts to mark and traverse context stacks without proper validation of object lifetimes, leading to use-after-free conditions where freed memory locations are accessed again. This memory corruption can result in application crashes, segmentation faults, or potentially more severe consequences depending on the execution environment. The vulnerability manifests as heap corruption that can be leveraged to disrupt normal application operation or potentially execute arbitrary code.
From an operational perspective, this vulnerability poses significant risks to systems running mruby applications, particularly those that process untrusted ruby script inputs or serve as embedded scripting engines. The denial of service impact can render applications unavailable to legitimate users, while the potential for unspecified other impacts suggests possibilities for privilege escalation or remote code execution depending on the deployment context. The vulnerability affects the core memory management functionality of mruby, making it particularly dangerous in environments where the interpreter handles dynamic code execution from external sources.
Security practitioners should prioritize patching affected mruby installations to version 1.2.1 or later, which contains the necessary fixes for the garbage collection memory management issues. Additionally, implementing input validation and sanitization measures for all ruby script processing can help mitigate the risk of exploitation. The vulnerability aligns with CWE-416, which describes use-after-free conditions, and represents a classic example of memory safety issues that can lead to both availability and integrity compromises. Organizations should also consider implementing runtime monitoring and application whitelisting to detect and prevent exploitation attempts against vulnerable systems.
The ATT&CK framework categorizes this vulnerability under the T1059.007 technique for Scripting, specifically targeting interpreter-based execution environments where untrusted code can be executed. This vulnerability demonstrates the critical importance of secure coding practices in memory management and the need for comprehensive testing of garbage collection mechanisms in interpreted languages. The exploitation potential makes this vulnerability particularly relevant for attackers seeking to compromise systems running mruby-based applications, especially in web applications or embedded systems where such interpreters are commonly deployed.