CVE-2019-3571 in WhatsApp Desktop
Summary
by MITRE
An input validation issue affected WhatsApp Desktop versions prior to 0.3.3793 which allows malicious clients to send files to users that would be displayed with a wrong extension.
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Analysis
by VulDB Data Team • 07/07/2020
The vulnerability identified as CVE-2019-3571 represents a critical input validation flaw within WhatsApp Desktop client software that existed in versions prior to 0.3.3793. This security weakness stems from inadequate sanitization of file extensions during the file transfer process, creating a scenario where malicious actors can manipulate file type indicators to deceive end users. The vulnerability specifically affects the desktop application's handling of file metadata, particularly the extension field that determines how files are displayed and processed by the user's operating system. When a user receives a file through this vulnerable client, the system may display the file with a misleading extension that does not match the actual file content, potentially leading to user confusion and security risks.
The technical implementation of this vulnerability involves the manipulation of file transfer protocols where the desktop client fails to properly validate the extension field in file metadata against the actual file content. This allows attackers to craft malicious file transfers where the displayed extension differs from the true file type, enabling social engineering attacks that rely on user trust in file type indicators. The flaw essentially creates a mismatch between what the user sees and what the system actually processes, exploiting the trust users place in visual file indicators. This issue falls under the CWE-20 category of "Improper Input Validation" and represents a specific instance of CWE-15 "Improper Neutralization of Input During Web Output" when considering the display layer of file handling.
The operational impact of this vulnerability extends beyond simple user confusion to potentially enable more sophisticated attack vectors. Users may be tricked into opening files with extensions that appear benign but actually contain malicious content, such as executable files disguised as image or document files. This creates opportunities for phishing attacks, malware distribution, and other social engineering campaigns that exploit user expectations about file types. The vulnerability particularly affects the desktop application's security model where file handling occurs locally on the user's machine, making it a client-side issue that can bypass network-level security controls. This weakness aligns with ATT&CK technique T1059.001 "Command and Scripting Interpreter: PowerShell" and T1068 "Exploitation for Privilege Escalation" when considering how attackers might leverage the misrepresentation to execute malicious code.
Mitigation strategies for CVE-2019-3571 primarily focus on updating to the patched version 0.3.3793 or later, which implements proper input validation and sanitization of file extensions. Organizations should enforce mandatory client updates through enterprise management systems and implement user education programs about the risks of opening files with suspicious extensions. Security teams should monitor for any attempts to exploit this vulnerability through file transfer channels and consider implementing additional validation layers at network boundaries. The fix typically involves strengthening the input validation process to ensure that file extensions match the actual content type and implementing proper sanitization of metadata fields before display. System administrators should also consider implementing file type restrictions and content scanning mechanisms that can detect and prevent the execution of potentially malicious files regardless of their displayed extensions. This vulnerability demonstrates the importance of proper input validation in client applications and highlights the need for comprehensive security testing that includes edge cases in file handling and user interface components.