CVE-2023-47168 in Mattermost
Summary
by MITRE • 11/27/2023
Mattermost fails to properly check a redirect URL parameter allowing for an open redirect was possible when the user clicked "Back to Mattermost" after providing a invalid custom url scheme in /oauth/{service}/mobile_login?redirect_to=
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Analysis
by VulDB Data Team • 12/16/2023
The vulnerability identified as CVE-2023-47168 represents a critical open redirect flaw within the Mattermost collaboration platform that stems from inadequate validation of redirect URL parameters during the OAuth mobile login process. This security weakness specifically manifests when users encounter invalid custom URL schemes and subsequently attempt to return to Mattermost through the "Back to Mattermost" functionality. The flaw resides in the /oauth/{service}/mobile_login endpoint where the redirect_to parameter fails to undergo proper sanitization or validation checks before being processed, creating an avenue for malicious actors to manipulate the redirection flow.
The technical implementation of this vulnerability allows attackers to craft malicious redirect URLs that could potentially lead users to phishing sites or malicious domains while maintaining the appearance of legitimate Mattermost navigation. When users click the "Back to Mattermost" button after encountering an invalid custom URL scheme, the system processes the redirect_to parameter without sufficient validation, enabling attackers to inject arbitrary URLs that will be executed upon user interaction. This behavior directly violates security best practices for input validation and redirect handling, creating a vector for social engineering attacks where users might be deceived into visiting malicious websites while believing they are returning to their legitimate Mattermost environment.
The operational impact of this vulnerability extends beyond simple redirection attacks as it creates potential for credential theft, malware distribution, and broader phishing campaigns targeting Mattermost users. Attackers could exploit this flaw to redirect users to sites that mimic the Mattermost interface, potentially capturing login credentials or other sensitive information. The vulnerability affects users who interact with the mobile OAuth login flow and could be particularly dangerous in enterprise environments where Mattermost serves as a primary communication platform. The flaw represents a significant risk to user security and organizational data integrity, as it enables attackers to manipulate user navigation without requiring additional authentication or authorization.
From a security framework perspective, this vulnerability aligns with CWE-601 Open Redirect vulnerability classification, which specifically addresses situations where applications redirect users to external domains without proper validation. The issue also maps to ATT&CK technique T1566.002 Phishing via Service Provider, as it enables attackers to create convincing phishing experiences through legitimate-looking redirects. Organizations using Mattermost should implement immediate mitigations including strict validation of redirect URLs, implementation of a whitelist approach for redirect destinations, and comprehensive input sanitization for all redirect parameters. Additionally, security teams should consider implementing additional monitoring for unusual redirect patterns and user behavior anomalies that might indicate exploitation attempts. The vulnerability underscores the critical importance of proper input validation and the principle of least privilege in redirect handling, emphasizing that all external inputs should be rigorously validated before being used in navigation decisions.