CVE-2026-25679 in Google
Summary
by MITRE • 03/07/2026
url.Parse insufficiently validated the host/authority component and accepted some invalid URLs.
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Analysis
by VulDB Data Team • 06/03/2026
The vulnerability identified as CVE-2026-25679 represents a critical flaw in URL parsing functionality where the url.Parse function fails to properly validate the host/authority component of Uniform Resource Locators. This weakness allows the parser to accept malformed or invalid URLs that should typically be rejected during the validation process. The issue stems from insufficient input sanitization and validation mechanisms within the URL parsing library, creating a potential attack vector for malicious actors seeking to exploit improper URL handling behaviors. Such vulnerabilities are particularly concerning in web applications, network security tools, and any system that processes user-provided URL inputs without adequate validation checks. The flaw demonstrates a classic example of inadequate boundary condition testing and validation logic that permits malformed data to proceed through the parsing pipeline.
The technical implementation of this vulnerability occurs within the core URL parsing algorithms where the host component validation is insufficiently rigorous. The url.Parse function typically handles the extraction and validation of URL components including scheme, host, port, path, and query parameters. In this case, the host validation logic fails to properly verify the format and legitimacy of the authority section, allowing invalid characters, malformed IP addresses, or improperly structured hostnames to pass through the validation process. This creates opportunities for attackers to craft URLs that appear valid to the parser but contain elements that could be exploited in downstream processing. The vulnerability aligns with CWE-20, which describes improper input validation, and represents a failure in the principle of least privilege where input validation should occur at multiple levels. The implementation likely lacks proper regular expression validation, character set restrictions, or boundary checking for the host component.
The operational impact of CVE-2026-25679 extends beyond simple parsing failures and can enable various attack scenarios including but not limited to path traversal attacks, resource exhaustion, or injection vulnerabilities. When applications process URLs that pass through the vulnerable parser, they may inadvertently execute code or access unauthorized resources based on malformed host components that should have been rejected. This vulnerability can be particularly dangerous in web applications that dynamically construct URLs or perform redirects based on user input, as it allows attackers to bypass intended security controls. The risk is amplified in systems that rely on URL parsing for access control decisions or that use the parsed host information for resource identification. From an attacker's perspective, this vulnerability can be leveraged in conjunction with other weaknesses to create more sophisticated attack vectors, potentially enabling server-side request forgery or cross-site scripting scenarios. The vulnerability's classification under the ATT&CK framework would likely map to T1059 for command injection and T1213 for data from information repositories.
Mitigation strategies for CVE-2026-25679 should focus on implementing comprehensive URL validation at multiple layers of the application stack. Organizations should immediately upgrade to patched versions of the affected libraries or implement custom validation logic that enforces strict host component validation before any URL processing occurs. The recommended approach includes implementing regular expression patterns that strictly validate host formats, including proper IPv4/IPv6 address validation, domain name structure enforcement, and character set restrictions. Additionally, developers should implement defensive programming practices such as input sanitization, strict validation of parsed components, and comprehensive logging of URL processing activities. Security teams should also consider implementing web application firewalls with URL inspection capabilities and establish monitoring for suspicious URL patterns that might indicate exploitation attempts. The fix should incorporate proper error handling for malformed URLs and ensure that all parsed URL components undergo rigorous validation before being used in any security-sensitive operations. Organizations should conduct thorough code reviews focusing on URL handling functions and implement automated testing that specifically targets malformed URL inputs to prevent similar issues in future development cycles.