CVE-2026-85622 in AppFlowy-Cloud
Summary
by MITRE • 09/04/2026
AppFlowy-Cloud through 0.9.64 fails to validate workspace membership when establishing WebSocket connections in the establish_ws_connection_v2 handler, allowing authenticated users to bind sessions to workspaces they do not belong to. Attackers can send sync Manifest messages with victim object identifiers to read full document or database state from collaborations in other workspaces without victim involvement.
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Analysis
by VulDB Data Team • 09/05/2026
The vulnerability identified in AppFlowy-Cloud versions through 0.9.64 represents a critical failure in access control mechanisms within the WebSocket connection establishment process. Specifically, the establish_ws_connection_v2 handler lacks proper validation of workspace membership before binding user sessions to specific workspaces. This architectural flaw allows authenticated users to bypass intended isolation boundaries between distinct collaborative environments. In secure multi-tenant applications or team-based collaboration platforms, it is imperative that every session initialization strictly verifies that the requesting entity possesses valid permissions for the target resource. The absence of this check creates a direct path for unauthorized access, undermining the fundamental security principle of least privilege and data segregation.
From a technical perspective, the flaw resides in the logic governing how WebSocket sessions are associated with workspace identifiers during the handshake or initial connection phase. When an authenticated user initiates a connection, the server accepts the requested workspace identifier without cross-referencing it against the user's actual membership list for that workspace. This oversight enables an attacker to manipulate client-side parameters to specify object identifiers belonging to other workspaces. Once the session is bound to these unauthorized resources, the application proceeds to synchronize data as if the connection were legitimate and authorized. The lack of server-side validation at this critical juncture means that subsequent operations relying on this session context inherit its invalid permissions, effectively granting the attacker full administrative-like access to the targeted workspace's collaborative state.
The operational impact of this vulnerability is severe, particularly regarding confidentiality and data integrity. Attackers can exploit this misconfiguration by sending sync Manifest messages containing victim object identifiers from workspaces they do not belong to. This action allows them to read the complete document or database state associated with those objects. Since collaboration platforms often contain sensitive intellectual property, personal information, or proprietary business logic, such unauthorized access constitutes a significant data breach. The attacker does not require any interaction from the legitimate victims; the exploitation is passive and silent once the connection is established. This capability effectively breaks the trust model of the application, allowing lateral movement across workspace boundaries without detection by standard audit logs that might only track valid session initiations rather than unauthorized resource access patterns.
This vulnerability aligns with CWE-284 Improper Access Control, specifically reflecting a failure to enforce proper authorization checks during resource initialization. It also maps closely to MITRE ATT&CK technique T1078 Valid Accounts, where an attacker uses legitimate credentials but abuses their privileges or configuration flaws to access unauthorized resources. Furthermore, the exploitation method of manipulating client-side inputs to affect server-side state without validation is characteristic of CWE-20 Improper Input Validation. The ability to read full document states from other workspaces highlights a critical gap in multi-tenancy security design, where logical separation between tenants must be enforced at every layer of the application stack, not just at high-level API endpoints but also within real-time communication channels like WebSockets.
Mitigation strategies should focus on implementing rigorous server-side validation for all workspace-related operations during session establishment. Developers must ensure that the establish_ws_connection_v2 handler explicitly queries the database or identity provider to verify that the authenticated user is a member of the requested workspace before binding any resources. This check should be performed atomically with the connection setup to prevent race conditions. Additionally, implementing strict input validation on all parameters passed during WebSocket initialization will help reject malformed or unauthorized requests early in the request lifecycle. Regular security audits and penetration testing focused on multi-tenant isolation are recommended to identify similar flaws in other parts of the application. Updating to a patched version that includes these access control checks is essential for restoring the integrity of collaborative data environments.