CVE-2023-2797 in Server
Summary
by MITRE • 06/16/2023
Mattermost fails to sanitize code permalinks, allowing an attacker to preview code from private repositories by posting a specially crafted permalink on a channel.
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Analysis
by VulDB Data Team • 07/14/2023
The vulnerability identified as CVE-2023-2797 represents a critical security flaw in the Mattermost collaboration platform that undermines the confidentiality of private code repositories. This issue stems from inadequate input sanitization mechanisms within the permalink handling functionality, creating an exploitable vector that allows unauthorized access to sensitive code content. The vulnerability specifically affects the code preview feature that users encounter when sharing links to specific code segments within Mattermost channels. When users post permalinks to code files, the application should properly validate and sanitize these references to ensure they point to authorized resources within the user's permitted scope.
The technical implementation flaw resides in the application's failure to properly validate the origins and permissions associated with code permalink references. Attackers can craft malicious permalinks that bypass normal access controls and allow preview of code from private repositories that should otherwise be restricted to authorized users only. This represents a classic case of insufficient input validation and access control enforcement, which falls under the CWE-20 category of "Improper Input Validation" and specifically relates to CWE-639 "Authorization Bypass Through User-Controlled Key." The vulnerability operates by exploiting the trust model between the Mattermost platform and its users, where legitimate permalink functionality is abused to gain unauthorized access to private code repositories.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally compromises the security model of private code repositories within Mattermost environments. Organizations relying on Mattermost for code collaboration and review may experience unauthorized access to sensitive source code, potentially exposing intellectual property, security configurations, and implementation details that should remain confidential. The attack vector is particularly concerning because it requires minimal technical expertise to exploit, as users only need to post a specially crafted permalink in a channel to potentially access private repository contents. This creates a persistent threat that can be leveraged by both external attackers and compromised internal users, making it particularly dangerous in enterprise environments where code repositories contain critical business logic and security-sensitive information.
Security professionals should consider this vulnerability in the context of broader ATT&CK framework categories including T1071.004 for Application Layer Protocol and T1566 for Phishing, as it enables attackers to gain access to code repositories through seemingly legitimate communication channels. The vulnerability also aligns with T1068 for Exploitation for Privilege Escalation, as it allows unauthorized users to access resources beyond their normal permissions. Organizations should implement immediate mitigations including enhanced input validation for permalink handling, stricter access controls for code preview features, and monitoring for suspicious permalink usage patterns. The remediation process should involve comprehensive code review of the permalink handling components, implementation of proper authentication and authorization checks, and potentially the introduction of rate limiting or additional verification steps for code preview requests. Additionally, security teams should conduct thorough assessments of their Mattermost environments to identify any other potential bypasses or similar vulnerabilities in the code preview and permalink functionality, ensuring that all user-generated content is properly sanitized and validated before being processed or displayed within the platform.
The vulnerability demonstrates the critical importance of proper input sanitization and access control enforcement in collaborative platforms that handle sensitive code repositories. It highlights how seemingly minor implementation flaws in user interface components can create significant security risks when dealing with privileged content access. Organizations should also consider implementing additional security controls such as content filtering, user behavior monitoring, and regular security assessments to prevent similar vulnerabilities from emerging in other components of their collaboration platforms. The incident underscores the necessity of treating all user-generated content as potentially malicious and implementing robust validation mechanisms throughout the application lifecycle.