CVE-2018-11743 in mruby
Summary
by MITRE
The init_copy function in kernel.c in mruby 1.4.1 makes initialize_copy calls for TT_ICLASS objects, which allows attackers to cause a denial of service (mrb_hash_keys uninitialized pointer and application crash) or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 03/21/2023
The vulnerability identified as CVE-2018-11743 resides within the mruby interpreter version 1.4.1, specifically within the kernel.c file's init_copy function. This flaw represents a critical security issue that affects the interpreter's handling of object initialization processes, particularly concerning TT_ICLASS objects which are internal class representations in the mruby runtime environment. The vulnerability stems from improper handling of initialize_copy method calls during object copying operations, creating a pathway for malicious exploitation that can lead to system instability and potential denial of service conditions.
The technical implementation of this vulnerability occurs when the init_copy function processes TT_ICLASS objects, which are used internally by mruby to represent class inheritance structures. During the copying process, the function invokes initialize_copy calls without proper validation of the object state, leading to scenarios where mrb_hash_keys remains uninitialized and subsequently triggers application crashes. This uninitialized pointer access represents a classic memory safety vulnerability that can be exploited by attackers to manipulate the interpreter's internal state. The flaw demonstrates poor input validation and inadequate error handling within the mruby core, as the system fails to properly verify object integrity before executing copy operations that involve internal class structures.
The operational impact of CVE-2018-11743 extends beyond simple denial of service conditions, potentially enabling more sophisticated attack vectors that could compromise system stability and availability. When exploited, the vulnerability can cause applications built on mruby to crash unpredictably, leading to service disruption and potential data loss. The uninitialized pointer access pattern suggests this vulnerability may also open doors to information disclosure or privilege escalation scenarios, depending on the specific execution context and application environment. This type of vulnerability is particularly concerning in server-side applications where mruby is used for web application scripting, as it could allow attackers to disrupt services or potentially gain unauthorized access to system resources. The impact aligns with CWE-476 which addresses NULL pointer dereferences and CWE-121 which covers stack-based buffer overflow conditions, both of which represent fundamental memory safety issues.
Mitigation strategies for CVE-2018-11743 should focus on immediate patching of the mruby interpreter to version 1.4.2 or later, which contains the necessary fixes for the init_copy function implementation. System administrators should also implement monitoring solutions to detect anomalous application behavior that may indicate exploitation attempts, particularly focusing on crash patterns and memory access violations. Additional defensive measures include restricting application privileges, implementing proper input validation for all user-supplied data, and utilizing runtime sandboxes to limit the potential impact of successful exploitation attempts. Organizations should also consider implementing intrusion detection systems that can identify patterns consistent with this vulnerability's exploitation methods, as defined in the ATT&CK framework's technique T1499 for resource hijacking and T1059 for command and scripting interpreter usage. The vulnerability highlights the importance of proper memory management and input validation in interpreted languages, emphasizing that even seemingly minor implementation flaws in core interpreter functions can have significant security implications across all applications built on that platform.