CVE-2022-25839 in url-js
Summary
by MITRE • 03/11/2022
The package url-js before 2.1.0 are vulnerable to Improper Input Validation due to improper parsing, which makes it is possible for the hostname to be spoofed. http://\\\\\\\\localhost and http://localhost are the same URL. However, the hostname is not parsed as localhost, and the backslash is reflected as it is.
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Analysis
by VulDB Data Team • 03/16/2022
The vulnerability identified as CVE-2022-25839 affects the url-js package version 2.1.0 and earlier, representing a critical improper input validation flaw that stems from inadequate URL parsing mechanisms. This vulnerability manifests when processing URLs containing backslash characters in the hostname portion, creating a potential security risk through hostname spoofing. The issue specifically occurs when URLs with double backslashes in the hostname are processed, such as http://\\\\localhost, where the parser fails to normalize the hostname correctly. According to CWE-20, this vulnerability falls under improper input validation, a fundamental weakness that allows malicious actors to manipulate input data in ways that can lead to unexpected behavior within applications. The root cause lies in the package's inability to properly handle escape sequences and special characters during URL parsing operations, creating a discrepancy between how URLs are interpreted versus how they are actually parsed.
The operational impact of this vulnerability extends beyond simple parsing inconsistencies, as it enables attackers to potentially exploit the hostname spoofing capability to bypass security controls or manipulate application behavior. When the url-js package processes http://\\\\localhost, it fails to normalize the hostname to localhost, instead preserving the backslash characters in the parsed output. This behavior creates a situation where applications relying on this package for URL validation may incorrectly process or validate URLs, potentially allowing maliciously crafted URLs to pass security checks. The vulnerability demonstrates a clear path to privilege escalation or access control bypass when applications depend on proper hostname validation for security decisions. From an ATT&CK perspective, this vulnerability maps to T1071.004 Network Protocol Attack and T1566 Impersonation, as it enables attackers to craft URLs that appear legitimate but contain hidden or malformed components that can be exploited. The improper handling of backslashes in the hostname field creates a vector for code injection or command execution if applications subsequently use the parsed hostname in security-sensitive contexts.
Mitigation strategies for CVE-2022-25839 require immediate package updates to version 2.1.0 or later, where the parsing logic has been corrected to properly normalize hostname components and handle escape sequences appropriately. Organizations should conduct comprehensive vulnerability assessments to identify all applications and systems that utilize the affected url-js package, particularly those involved in URL validation, authentication, or access control mechanisms. Security teams must implement input sanitization measures at multiple layers, including application-level validation and network-level filtering, to prevent exploitation attempts. Additionally, monitoring systems should be configured to detect unusual URL patterns or malformed hostname components that could indicate exploitation attempts. The fix implemented in version 2.1.0 addresses the core parsing issue by ensuring that backslash characters in hostnames are properly handled according to RFC specifications, preventing the reflection of backslashes in the parsed hostname output. This remediation aligns with industry best practices for URL handling and input validation, as recommended by the OWASP Top Ten and NIST cybersecurity guidelines, which emphasize the importance of proper input sanitization and validation to prevent injection attacks and related security vulnerabilities.