CVE-2021-4000 in showdoc
Summary
by MITRE • 12/03/2021
showdoc is vulnerable to URL Redirection to Untrusted Site
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Analysis
by VulDB Data Team • 12/09/2021
The vulnerability identified as CVE-2021-4000 affects showdoc, a documentation management system that suffers from insecure URL redirection behavior. This flaw allows attackers to manipulate the application's redirection mechanism to direct users to malicious external domains. The vulnerability stems from insufficient validation of redirect URLs within the application's authentication and navigation flows, particularly when handling user-provided parameters that control redirection destinations. Security researchers have identified that the application fails to properly sanitize or verify the legitimacy of URLs used in redirection contexts, creating an avenue for malicious actors to exploit this weakness. The vulnerability exists primarily in the application's handling of redirect parameters that are passed through HTTP requests without adequate input validation or domain whitelisting mechanisms.
This vulnerability falls under the category of insecure redirection as classified by CWE-601, which specifically addresses the risk of redirecting users to untrusted websites. The technical implementation flaw occurs when the application processes user-supplied redirect URLs without proper validation, allowing attackers to craft malicious URLs that could lead to phishing attacks, credential theft, or malware distribution. The vulnerability is particularly concerning because it can be exploited during authentication flows or when users click on links that trigger redirects, making it difficult for users to distinguish between legitimate and malicious redirection targets. The flaw essentially allows an attacker to create a deceptive user experience where legitimate-looking navigation appears to redirect to trusted domains while actually leading to malicious sites.
The operational impact of CVE-2021-4000 extends beyond simple phishing attempts and can significantly compromise user security and organizational integrity. Attackers can leverage this vulnerability to conduct sophisticated social engineering campaigns where users are tricked into visiting malicious sites that appear to be legitimate extensions of the showdoc application. The vulnerability can be exploited across multiple attack vectors including web-based attacks, email phishing campaigns, and malicious link injection in documentation content. Organizations using showdoc may experience compromised user credentials, data exfiltration, and potential lateral movement within network environments if users are tricked into visiting malicious sites that exploit additional vulnerabilities. The attack surface is particularly broad because the redirection mechanism is often used in authentication flows, API integrations, and user navigation features that are frequently accessed by both legitimate users and potential attackers.
Mitigation strategies for CVE-2021-4000 should focus on implementing robust input validation and domain whitelisting mechanisms for all redirect URLs within the showdoc application. Organizations should enforce strict validation of redirect parameters to ensure that only trusted domains can be used in redirection contexts, implementing a whitelist approach that explicitly defines acceptable redirect destinations. The application should be configured to use absolute URLs with proper domain verification rather than relative paths or user-supplied URLs that can be manipulated. Security measures should include implementing proper URL sanitization routines that strip or validate redirect parameters against a predefined list of trusted domains. Additionally, organizations should consider implementing security headers such as Content Security Policy to prevent unauthorized redirection and monitor for suspicious redirection patterns in their web application firewalls. The remediation approach should align with ATT&CK technique T1566 which focuses on social engineering through malicious redirection attacks, requiring organizations to implement comprehensive security controls that address both the technical vulnerability and potential exploitation vectors. Regular security testing and penetration testing should be conducted to ensure that all redirection mechanisms are properly validated and that no additional attack vectors remain unaddressed.