CVE-2022-31246 in Electrum
Summary
by MITRE • 06/17/2022
paymentrequest.py in Electrum before 4.2.2 allows a file:// URL in the r parameter of a payment request (e.g., within QR code data). On Windows, this can lead to capture of credentials over SMB. On Linux and UNIX, it can lead to a denial of service by specifying the /dev/zero filename.
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Analysis
by VulDB Data Team • 06/17/2022
The vulnerability identified as CVE-2022-31246 affects the Electrum cryptocurrency wallet software version 4.2.1 and earlier, specifically within the paymentrequest.py module. This flaw represents a critical security oversight that enables malicious actors to exploit the wallet's handling of payment request URLs, particularly those containing file:// schemes in the r parameter. The vulnerability stems from insufficient validation of URL schemes and file paths within payment requests, creating potential attack vectors that vary significantly based on the operating system environment. The issue manifests when users scan QR codes or otherwise process payment requests that contain specially crafted file:// URLs, which the software processes without adequate sanitization or security checks.
The technical implementation of this vulnerability involves the improper handling of file:// URLs within the payment request processing pipeline. When Electrum encounters a payment request containing a file:// URL in the r parameter, it fails to validate whether the specified file path is legitimate or safe for access. On Windows systems, this creates a particularly dangerous scenario where the software can be tricked into accessing network resources via SMB protocols, potentially allowing attackers to capture authentication credentials through malicious file paths that resolve to network shares or other accessible resources. The vulnerability leverages the trust model inherent in payment request processing, where users expect the system to automatically handle and validate all components of a payment request without additional user intervention. This flaw falls under CWE-22, known as "Improper Limitation of a Pathname to a Restricted Directory," and represents a classic path traversal vulnerability that has been exploited in similar contexts across various software platforms.
The operational impact of CVE-2022-31246 varies significantly across different operating systems due to the platform-specific nature of file access mechanisms and network protocols. On Windows platforms, the vulnerability enables credential theft through SMB network access, potentially allowing attackers to capture authentication information from users who process malicious payment requests. This attack vector aligns with ATT&CK technique T1075, "Pass the Hash," where attackers exploit legitimate authentication mechanisms to gain unauthorized access. On Linux and UNIX systems, the vulnerability results in a denial of service condition where attackers can specify /dev/zero as a file path, causing the wallet application to consume excessive system resources or enter an unstable state. The difference in impact between platforms demonstrates how the same underlying vulnerability can manifest differently based on system architecture and file system behavior, with Windows presenting more severe security implications due to its network protocol handling capabilities.
Mitigation strategies for CVE-2022-31246 focus primarily on updating to Electrum version 4.2.2 or later, which includes proper validation of URL schemes and file paths within payment requests. Security professionals should implement additional protective measures such as disabling automatic payment request processing in high-risk environments, educating users about the dangers of scanning unknown QR codes, and monitoring for suspicious network activity that might indicate credential theft attempts. The vulnerability highlights the importance of input validation and secure coding practices, particularly when handling user-provided data that may contain embedded protocols or file references. Organizations should also consider implementing network-based monitoring to detect potential SMB access attempts from wallet applications and establish proper access controls to prevent unauthorized network resource access. This vulnerability serves as a reminder of the critical need for robust validation of external inputs and the potential for seemingly benign features to become attack vectors when proper security controls are not implemented. The fix implemented in Electrum 4.2.2 demonstrates the importance of proper URL scheme validation and the need for applications to enforce strict boundaries when processing external data, particularly in financial applications where user security is paramount.