CVE-2019-19648 in YARA
Summary
by MITRE
In the macho_parse_file functionality in macho/macho.c of YARA 3.11.0, command_size may be inconsistent with the real size. A specially crafted MachO file can cause an out-of-bounds memory access, resulting in Denial of Service (application crash) or potential code execution.
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Analysis
by VulDB Data Team • 03/09/2024
The vulnerability identified as CVE-2019-19648 resides within the macho_parse_file function in the macho/macho.c file of YARA version 3.11.0, representing a critical security flaw that undermines the integrity of the application's binary parsing capabilities. This issue specifically affects the handling of MachO (Mach Object) files, which are the standard binary format used by macOS and iOS operating systems for executables, object code, and shared libraries. The vulnerability stems from an inconsistent command_size parameter that fails to properly validate the actual size of MachO commands, creating a scenario where maliciously crafted files can exploit this discrepancy to manipulate memory access patterns.
The technical flaw manifests when the parsing logic encounters a MachO file with manipulated command_size values that do not align with the actual data structure sizes present in the file. This inconsistency creates a memory access boundary violation where the application attempts to read or write beyond allocated memory regions. The flaw operates at the intersection of buffer management and input validation, where the parser assumes command_size accurately reflects the subsequent data structure size without proper verification mechanisms. When processing malformed MachO files, the application's memory management becomes compromised, leading to unpredictable behavior that can manifest as application crashes or more severe consequences including potential code execution.
From an operational perspective, this vulnerability presents a significant risk to systems that utilize YARA for malware detection, threat hunting, or binary analysis operations. The Denial of Service aspect means that legitimate security operations could be disrupted by adversaries who craft malicious MachO files designed to crash YARA processes, effectively disabling threat detection capabilities. The potential for code execution represents an even more serious concern, as it could allow attackers to gain unauthorized control over systems running vulnerable versions of YARA. This vulnerability particularly impacts security analysts and organizations that rely on YARA for automated binary analysis, as it creates an attack surface where adversarial payloads could be designed to exploit this parsing flaw during routine security operations.
The vulnerability aligns with CWE-129, which addresses improper validation of array index and buffer bounds, and demonstrates characteristics consistent with CWE-787, improper access to memory beyond the bounds of a buffer. Additionally, this issue can be categorized under ATT&CK technique T1059.007 for command and scripting interpreter, as it could enable adversaries to execute arbitrary code through manipulated binary files that bypass normal validation checks. The exploitation scenario typically involves crafting a MachO file with intentionally malformed command_size values that cause the parsing routine to access invalid memory locations, potentially leading to stack corruption or heap manipulation.
Mitigation strategies should prioritize immediate patching to YARA version 3.12.0 or later, where this vulnerability has been addressed through enhanced input validation and proper bounds checking mechanisms. Organizations should implement additional safeguards such as sandboxing YARA processes during binary analysis operations, implementing strict file validation protocols before processing, and monitoring for unusual memory access patterns that might indicate exploitation attempts. Security teams should also consider implementing network-based detection rules that identify suspicious MachO file patterns and ensure that all systems running YARA have up-to-date security patches applied. The fix typically involves adding proper validation checks that verify command_size values against actual data structure sizes before proceeding with memory operations, thereby preventing the out-of-bounds access that leads to the vulnerability's exploitation.