CVE-2022-29159 is a medium-severity authorization bypass vulnerability affecting Nextcloud Deck, a Kanban-style project and personal management application integrated with the Nextcloud platform. The vulnerability exists in versions prior to 1.4.8, between 1.5.0 and 1.5.6 (exclusive), and specifically version 1.6.0. The issue arises from improper authorization checks when handling user-controlled keys that identify boards and stacks within the Deck application. An authenticated user can exploit this flaw to move stacks containing cards from their own board to another user's board without proper permission. This behavior violates the principle of least privilege and allows unauthorized modification of another user's project boards. The vulnerability is classified under CWE-639, which relates to authorization bypass through user-controlled keys. The flaw was patched in versions 1.4.8, 1.5.6, and 1.6.1 of Nextcloud Deck. There are no known workarounds available, and no exploits have been reported in the wild to date. The vulnerability requires the attacker to be authenticated, meaning they must have valid user credentials on the Nextcloud instance. However, no additional user interaction beyond authentication is necessary to exploit the flaw. The impact primarily concerns the integrity and confidentiality of project management data within Nextcloud Deck, as unauthorized users can manipulate other users' boards, potentially leading to data tampering or disruption of collaborative workflows.

For European organizations using Nextcloud Deck for project management, this vulnerability poses a risk to the integrity and confidentiality of internal project data. Unauthorized modification of boards can disrupt team collaboration, cause loss of trust in project tracking, and potentially expose sensitive project information if boards contain confidential data. Organizations in sectors with strict data protection regulations, such as finance, healthcare, and government, may face compliance risks if unauthorized data manipulation occurs. Additionally, the vulnerability could be leveraged by insider threats or compromised user accounts to escalate privileges within the project management context. While the vulnerability does not directly affect system availability, the disruption to project workflows can indirectly impact operational efficiency. Since Nextcloud is widely adopted in Europe, especially among privacy-conscious organizations and public institutions favoring open-source solutions, the impact could be significant in environments where Deck is actively used for managing sensitive projects.

1. Immediate upgrade of Nextcloud Deck to versions 1.4.8, 1.5.6, or 1.6.1 or later is the primary mitigation step to remediate this vulnerability. 2. Conduct an audit of user permissions and project boards to detect any unauthorized modifications that may have occurred prior to patching. 3. Implement strict access controls and monitoring on Nextcloud instances, including multi-factor authentication (MFA) to reduce the risk of compromised user credentials. 4. Limit the number of users with access to project boards and enforce the principle of least privilege to minimize potential exploitation impact. 5. Monitor Nextcloud logs for unusual activity related to board modifications or stack movements to detect potential exploitation attempts. 6. Educate users about the importance of safeguarding their credentials and recognizing suspicious activity within the Nextcloud environment. 7. For organizations with custom integrations or automation interacting with Nextcloud Deck, review and update these to ensure they do not inadvertently bypass authorization checks. 8. Engage with Nextcloud community or vendor support to stay informed about any emerging threats or additional patches related to this vulnerability.