CVE-2018-19976 in YARA
Summary
by MITRE
In YARA 3.8.1, bytecode in a specially crafted compiled rule is exposed to information about its environment, in libyara/exec.c. This is a consequence of the design of the YARA virtual machine.
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Analysis
by VulDB Data Team • 06/19/2023
CVE-2018-19976 represents a significant information disclosure vulnerability within the YARA threat hunting and malware detection framework version 3.8.1. This vulnerability stems from the YARA virtual machine implementation in the libyara/exec.c component where bytecode from maliciously crafted compiled rules can potentially expose environmental information to attackers. The flaw exists at the core execution engine level of YARA's virtual machine architecture, making it particularly concerning for security analysts and organizations that rely on YARA for threat detection and malware analysis operations.
The technical nature of this vulnerability resides in how the YARA virtual machine processes and executes compiled bytecode rules. When YARA encounters specially crafted compiled rules containing malicious bytecode, the execution environment inadvertently leaks information about the host system or execution context. This occurs due to design decisions in the virtual machine implementation that fail to properly isolate the execution environment from sensitive information exposure. The vulnerability specifically affects the libyara/exec.c file, which serves as the primary execution engine for YARA's compiled rules, making it a critical component in the attack surface.
The operational impact of CVE-2018-19976 extends beyond simple information disclosure, as it can potentially enable attackers to gather intelligence about target systems and their configurations. This information leakage could be leveraged by adversaries to refine subsequent attacks or to understand the environment in which YARA is operating. Security professionals using YARA for malware analysis, incident response, or threat hunting operations face significant risks when encountering malicious YARA rules that exploit this vulnerability. The vulnerability affects organizations that process untrusted YARA rules or execute rules from unknown sources, as these scenarios create opportunities for exploitation.
Organizations should prioritize immediate mitigation by upgrading to YARA versions that address this vulnerability, as the flaw exists in the fundamental execution engine of the framework. The recommended approach involves implementing strict rule validation and sanitization procedures for any YARA rules that originate from untrusted sources. Additionally, system administrators should consider implementing network segmentation and access controls to limit the potential impact of exploitation. This vulnerability aligns with CWE-200, Information Exposure, and maps to ATT&CK technique T1059.007 for execution through scripting languages, as the exploitation involves manipulating the execution environment through crafted bytecode. The security community should treat this vulnerability as a high-priority issue requiring immediate attention and remediation across all YARA installations.