CVE-2020-15270 in parse-server
Summary
by MITRE • 10/23/2020
Parse Server (npm package parse-server) broadcasts events to all clients without checking if the session token is valid. This allows clients with expired sessions to still receive subscription objects. It is not possible to create subscription objects with invalid session tokens. The issue is not patched.
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Analysis
by VulDB Data Team • 11/26/2020
The vulnerability identified as CVE-2020-15270 affects Parse Server, a popular Node.js backend framework used for building mobile and web applications. This security flaw resides in the server's event broadcasting mechanism where the system fails to validate session tokens before transmitting subscription updates to connected clients. The issue represents a significant authorization bypass vulnerability that undermines the integrity of the application's user session management system.
The technical implementation of this vulnerability stems from the Parse Server's failure to perform proper session validation when broadcasting events to subscribed clients. When a client establishes a subscription to specific data changes, the server should verify that the associated session token remains valid before sending any updates. However, the current implementation broadcasts events to all connected clients regardless of their session status, including those with expired or invalid tokens. This flaw allows malicious actors with access to expired session tokens to continue receiving real-time updates from the server, effectively maintaining unauthorized access to data streams.
From an operational perspective, this vulnerability creates a persistent security risk where compromised or expired sessions can be exploited to maintain unauthorized access to application data. Attackers who obtain expired session tokens can continue to receive subscription events, potentially gaining access to sensitive information that should only be available to authenticated users with valid sessions. The vulnerability is particularly concerning in environments where real-time data synchronization is critical, as it enables continuous data leakage through unauthorized subscription channels.
The impact of this vulnerability extends beyond simple information disclosure, as it can facilitate further attacks including data exfiltration, privilege escalation, and persistent access to application resources. The lack of patching for this issue means that affected systems remain vulnerable indefinitely, creating a persistent threat vector for attackers who can leverage expired sessions to maintain access to subscription-based data flows. This vulnerability aligns with CWE-284 Access Control Issues, specifically addressing inadequate access control mechanisms that allow unauthorized access to protected resources through improper session validation.
Organizations affected by this vulnerability should implement immediate mitigations including enforcing strict session validation before event broadcasting, implementing robust session token expiration mechanisms, and monitoring subscription activities for unauthorized access patterns. The ATT&CK framework categorizes this issue under privilege escalation and persistence tactics, as attackers can maintain access through expired sessions. Recommended solutions include upgrading to patched versions of Parse Server, implementing additional authentication layers, and establishing monitoring protocols to detect anomalous subscription behavior. Without proper remediation, this vulnerability creates a persistent backdoor that can be exploited to maintain unauthorized access to application data streams.