CVE-2019-14809 in Google
Summary
by MITRE
net/url in Go before 1.11.13 and 1.12.x before 1.12.8 mishandles malformed hosts in URLs, leading to an authorization bypass in some applications. This is related to a Host field with a suffix appearing in neither Hostname() nor Port(), and is related to a non-numeric port number. For example, an attacker can compose a crafted javascript:// URL that results in a hostname of google.com.
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Analysis
by VulDB Data Team • 05/20/2025
The vulnerability identified as CVE-2019-14809 represents a critical authorization bypass issue within the Go programming language's net/url package affecting versions prior to 1.11.13 and 1.12.8. This flaw stems from improper handling of malformed host specifications within URLs, creating a security gap that can be exploited by malicious actors to circumvent authentication mechanisms in affected applications. The vulnerability manifests when applications rely on URL parsing for access control decisions, particularly in scenarios involving cross-origin resource sharing or web application security checks. The technical root cause lies in how the Host field processes suffixes that appear in neither the Hostname() nor Port() methods, creating inconsistencies in URL component extraction that can be manipulated by attackers.
The operational impact of this vulnerability extends beyond simple URL parsing errors to encompass serious security implications for applications that perform authorization checks based on URL hostnames or ports. When an attacker crafts a malicious javascript:// URL with a hostname of google.com, the system may incorrectly interpret the URL structure, leading to bypass of security controls that should prevent access to certain resources. This behavior creates a pathway for privilege escalation or unauthorized access to protected resources, particularly in applications that use URL-based access control lists or origin validation mechanisms. The vulnerability is particularly dangerous in web applications that implement CORS policies or perform security checks based on the hostname component of URLs, as it allows attackers to manipulate these checks through carefully constructed malformed URLs.
The technical flaw specifically relates to CWE-20, which addresses improper input validation, and demonstrates characteristics consistent with CWE-347, concerning improper verification of cryptographic signatures, though in this case the weakness manifests in URL parsing rather than cryptographic operations. From an ATT&CK framework perspective, this vulnerability maps to T1078, which covers valid accounts and T1566, concerning malicious input, as it enables attackers to exploit legitimate URL parsing mechanisms to bypass security controls. The issue is particularly relevant to applications implementing web security measures that rely on URL components for access control decisions, making it a significant concern for web application firewalls, content security policies, and origin-based security controls.
Mitigation strategies for CVE-2019-14809 require immediate patching of affected Go versions to the recommended secure releases, specifically upgrading to Go 1.11.13 or 1.12.8 and later. Organizations should also implement additional defensive measures including comprehensive URL validation routines that explicitly check for malformed host specifications, regular security scanning of applications that utilize URL parsing for authorization decisions, and implementation of additional access control layers beyond simple hostname-based checks. Network monitoring should be enhanced to detect unusual URL patterns that might indicate exploitation attempts, while application developers should review their code for reliance on potentially vulnerable URL parsing functions and implement proper input sanitization. Security teams should also consider implementing runtime protections that can detect and block suspicious URL patterns that could exploit this vulnerability, particularly in environments where patching timelines are extended. The vulnerability underscores the importance of thorough input validation and the potential security implications of seemingly benign parsing functions that may be leveraged in authorization bypass scenarios.