CVE-2022-28923 in Caddy
Summary
by MITRE • 02/07/2023
Caddy v2.4.6 was discovered to contain an open redirection vulnerability which allows attackers to redirect users to phishing websites via crafted URLs.
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Analysis
by VulDB Data Team • 03/26/2025
The vulnerability identified as CVE-2022-28923 represents a critical open redirection flaw within Caddy web server version 2.4.6. This issue stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied URLs, creating a pathway for malicious actors to craft deceptive links that appear legitimate while redirecting users to attacker-controlled domains. The vulnerability specifically affects the web server's handling of redirect directives and URL parsing functions, where user-provided parameters are not sufficiently validated before being used in redirection operations. The flaw enables attackers to exploit the server's redirect functionality to channel users toward phishing websites, credential harvesting pages, or other malicious destinations without proper authorization or user consent.
From a technical perspective, this vulnerability operates at the application layer and manifests as a failure in proper URL validation and sanitization. The underlying issue typically involves the web server's inability to distinguish between trusted internal redirects and potentially malicious external URLs, allowing crafted inputs to bypass security checks. The vulnerability can be triggered through various means including direct URL manipulation, parameter injection, or manipulation of redirect configurations. The flaw aligns with CWE-601 Open Redirect vulnerability classification, which specifically addresses situations where applications redirect users to untrusted destinations without proper validation. This weakness creates an attack surface that enables social engineering campaigns and phishing operations to leverage legitimate web server functionality for malicious purposes.
The operational impact of CVE-2022-28923 extends beyond simple redirection attacks, as it can facilitate sophisticated phishing campaigns that exploit user trust in legitimate web services. Attackers can craft URLs that appear to originate from trusted domains, making it difficult for users to distinguish between genuine and malicious redirects. This vulnerability particularly affects organizations that rely on Caddy for serving dynamic content or implementing redirect-based navigation systems, potentially exposing sensitive user data, enabling credential theft, or serving as a stepping stone for more complex attacks. The impact is amplified when the vulnerable server handles authentication flows, user registration processes, or any service that might redirect users to external domains. Security researchers have noted that such vulnerabilities often serve as initial access vectors in larger attack chains, as demonstrated by ATT&CK technique T1566.001 Phishing, where open redirect vulnerabilities are commonly leveraged to deliver malicious payloads through deceptive user interactions.
Mitigation strategies for this vulnerability should include immediate patching to version 2.4.7 or later, which contains the necessary fixes for URL validation and sanitization. Organizations should implement comprehensive input validation policies that explicitly check all redirect destinations against trusted domain lists and reject any external URLs that do not meet security criteria. Network administrators should consider implementing additional layers of protection including web application firewalls that can detect and block suspicious redirect patterns, and DNS-level controls that prevent resolution of potentially malicious domains. Security teams should also conduct thorough audits of all redirect configurations within their Caddy deployments, ensuring that only trusted internal destinations are permitted. The vulnerability serves as a reminder of the critical importance of validating all user inputs and implementing proper access controls, as outlined in the OWASP Top Ten and NIST cybersecurity frameworks. Regular security testing including penetration testing and vulnerability scanning should be implemented to identify similar issues in other web server configurations and application components.