CVE-2018-19974 in YARA
Summary
by MITRE
In YARA 3.8.1, bytecode in a specially crafted compiled rule can read uninitialized data from VM scratch memory in libyara/exec.c. This can allow attackers to discover addresses in the real stack (not the YARA virtual stack).
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Analysis
by VulDB Data Team • 06/19/2023
The vulnerability CVE-2018-19974 represents a critical memory safety issue within the YARA threat hunting framework version 3.8.1. This flaw exists in the bytecode execution engine of libyara, specifically within the exec.c file where the virtual machine processes compiled rules. The vulnerability stems from improper handling of uninitialized memory within the YARA virtual machine's scratch memory area, creating a potential information disclosure channel that could be exploited by malicious actors.
The technical implementation of this vulnerability occurs when YARA processes specially crafted compiled rules that contain bytecode designed to access uninitialized memory locations within the virtual machine's scratch space. This memory area, intended for temporary storage during bytecode execution, contains data that has not been properly initialized before being read. When the virtual machine executes these malicious bytecode sequences, it can inadvertently expose contents from the actual system stack memory, including memory addresses and potentially sensitive data structures that should remain private to the application's execution context.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can provide attackers with valuable insights into the memory layout of the running YARA process. This information disclosure capability aligns with CWE-248, an unspecified weakness in the context of uninitialized memory access, and can be leveraged as a stepping stone for more sophisticated attacks. The exposure of stack addresses can aid in bypassing memory protection mechanisms such as stack canaries and address space layout randomization, making subsequent exploitation attempts more likely to succeed. Attackers could potentially use this information to craft more effective buffer overflow exploits or other memory corruption attacks against the YARA framework.
From an adversarial perspective, this vulnerability fits within the ATT&CK framework under the technique T1059.007 for command and scripting interpreter, specifically in the context of process injection and memory manipulation. The ability to read uninitialized data from scratch memory creates opportunities for attackers to perform reconnaissance activities against the YARA process, potentially identifying memory layout characteristics that could be used in advanced exploitation techniques. This vulnerability demonstrates the importance of proper memory initialization practices and the potential consequences of inadequate bounds checking in virtual machine implementations.
The recommended mitigation strategy involves upgrading to a patched version of YARA where the uninitialized memory access has been addressed through proper initialization of scratch memory areas and implementation of bounds checking mechanisms. System administrators should also implement runtime monitoring to detect anomalous bytecode execution patterns that could indicate exploitation attempts. Additionally, organizations should consider implementing network segmentation and access controls to limit the potential impact of any successful exploitation attempts, while ensuring that compiled YARA rules are validated and sanitized before execution in production environments. The vulnerability serves as a reminder of the critical importance of memory safety practices in security tools, particularly those operating in environments where they process untrusted input data.