CVE-2026-104969 in Plane
Summary
by MITRE • 10/05/2026
Plane is an open-source project management tool. Prior to 1.4.0, the cycle-issues endpoint accepts issue UUIDs in the request body without validating that they belong to the caller's workspace. An authenticated user can add issues from any workspace to a cycle they control. If a victim issue is already assigned to a cycle, the operation removes it from the victim's cycle, causing a destructive cross-tenant write. This issue is fixed in 1.4.0.
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Analysis
by VulDB Data Team • 10/05/2026
The vulnerability identified in Plane versions prior to 1.4.0 represents a critical failure in access control mechanisms within an open-source project management platform. Specifically, the flaw resides in the cycle-issues endpoint, which is designed to manage the association of issues with specific development cycles or sprints. The core technical deficiency lies in the server-side validation logic, where the application accepts issue Universally Unique Identifiers (UUIDs) submitted by authenticated users but fails to verify that these target issues belong to the same workspace as the requesting user's cycle. This oversight creates a direct path for unauthorized cross-tenant operations, allowing an attacker with valid credentials on one tenant or workspace to manipulate resources belonging to entirely different tenants within the multi-tenancy architecture of the application.
From a technical perspective, this is a classic example of Insecure Direct Object Reference (IDOR) combined with Broken Access Control. The API endpoint trusts client-supplied identifiers without performing necessary authorization checks against the backend database relationships that link issues to workspaces and cycles. When an authenticated user submits a request containing UUIDs for issues located in other workspaces, the application processes these requests as if they were valid local operations. This lack of strict boundary enforcement between tenants undermines the fundamental security principle of isolation required in multi-tenant SaaS environments, where data integrity and confidentiality must be strictly maintained across organizational boundaries regardless of user authentication status.
The operational impact of this vulnerability is severe due to its destructive nature. If a victim issue is currently assigned to a cycle within its own workspace, an attacker can exploit this flaw by adding that same issue UUID to a cycle they control in their own workspace. The application logic appears to handle the assignment process such that it removes the issue from any existing cycle before assigning it to the new one. Consequently, this action effectively strips the victim's team of visibility into critical work items and disrupts sprint planning or workflow tracking for other organizations sharing the same Plane instance. This constitutes a destructive cross-tenant write operation, potentially leading to significant operational disruption, loss of productivity, and erosion of trust in the platform's data integrity among enterprise customers who rely on strict tenant isolation.
This vulnerability aligns with CWE-284 Improper Access Control and CWE-639 Authorization Bypass Through User-Controlled Key, as it allows an actor to bypass authorization checks by manipulating object identifiers. In terms of offensive security frameworks, this behavior maps directly to the MITRE ATT&CK technique T1078 Valid Accounts, where authenticated users are leveraged for lateral movement or privilege escalation across system boundaries, and specifically relates to data manipulation tactics that compromise availability and integrity rather than just confidentiality. The exploitation does not require complex injection techniques but relies on simple API misuse enabled by poor server-side validation.
To mitigate this vulnerability, organizations running Plane versions prior to 1.4.0 must upgrade immediately to version 1.4.0 or later, where the issue has been resolved through enhanced input validation and strict workspace-scoped authorization checks. For environments that cannot be patched instantly due to operational constraints, temporary mitigations should focus on network-level controls such as Web Application Firewalls (WAF) configured to detect anomalous patterns of cross-tenant API calls, although this is less reliable than a code fix. Additionally, implementing rigorous audit logging for all cycle and issue modification endpoints can aid in the rapid detection of exploitation attempts by monitoring for unusual spikes in requests involving UUIDs from disparate workspaces. Long-term architectural improvements should include enforcing workspace context validation at every layer of the application stack to ensure that no operation proceeds without verifying tenant ownership of both source and target resources.