CVE-2018-19975 in YARA
Summary
by MITRE
In YARA 3.8.1, bytecode in a specially crafted compiled rule can read data from any arbitrary address in memory, in libyara/exec.c. Specifically, OP_COUNT can read a DWORD.
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Analysis
by VulDB Data Team • 06/19/2023
The vulnerability identified as CVE-2018-19975 represents a critical memory safety issue within the YARA threat detection engine version 3.8.1. This flaw exists in the libyara/exec.c component where compiled bytecode rules can be manipulated to access arbitrary memory addresses through improper validation mechanisms. The vulnerability specifically affects the OP_COUNT instruction which is designed to count occurrences of patterns within scanned data but can be exploited to read DWORD values from any memory location accessible to the executing process.
This memory access violation stems from insufficient bounds checking and validation within the bytecode interpreter of YARA's execution engine. When a maliciously crafted compiled rule is executed, the OP_COUNT operation bypasses normal memory access controls and can traverse memory segments that should remain protected from direct inspection. The vulnerability enables an attacker to potentially extract sensitive information from memory including but not limited to cryptographic keys, credentials, application data, or system configuration details that might be stored in accessible memory regions.
The operational impact of this vulnerability extends beyond simple information disclosure as it can facilitate more sophisticated attacks by providing adversaries with insights into memory layout and application state. Attackers could leverage this capability to identify memory addresses of critical functions, data structures, or security-related variables that could then be used to craft further exploits or bypass security controls. The vulnerability affects systems running YARA 3.8.1 where compiled rules are executed, particularly in environments where threat detection systems process untrusted rule sets from external sources.
From a cybersecurity perspective, this vulnerability maps to CWE-125: Out-of-Bounds Read which is categorized under memory safety issues in the Common Weakness Enumeration framework. The attack pattern aligns with techniques described in MITRE ATT&CK framework under T1059.007: Command and Scripting Interpreter: Python, as exploitation may involve crafting malicious Python-based rule files that get compiled into bytecode. Additionally, the vulnerability demonstrates characteristics of T1555: Credentials from Password Stores which could be exploited to extract sensitive information from memory. The flaw represents a significant concern for organizations using YARA for malware detection, as it could be exploited to bypass security controls or extract information from systems running vulnerable versions.
Mitigation strategies should focus on immediate patching of YARA to version 3.9.0 or later where this vulnerability has been addressed through improved bounds checking and memory access validation. Organizations should also implement strict rule validation procedures for any compiled rules that are executed within their security infrastructure, particularly those received from external sources or third-party vendors. Additional protective measures include running YARA processes with minimal privileges, implementing memory protection mechanisms such as address space layout randomization, and monitoring for anomalous memory access patterns that might indicate exploitation attempts. Security teams should also consider isolating rule execution environments and implementing sandboxing techniques to limit the potential impact of any successful exploitation attempts.