CVE-2022-31024 is a medium-severity vulnerability affecting the richdocuments app, which is the repository for Nextcloud Collabora—an office collaboration tool integrated within Nextcloud. The vulnerability arises from improper access control (CWE-284) combined with origin validation errors (CWE-346). Specifically, in versions prior to 6.0.0, 5.0.4, and 4.2.6, a malicious actor can exploit federated sharing functionality to trick a user into interacting with a remote Office instance controlled by the attacker. This could lead to unauthorized actions being performed on behalf of the user without their full consent or awareness. The issue stems from insufficient validation of federated shares, allowing an attacker to craft a share that causes the victim's client to work against a remote, potentially malicious, Office server. The vulnerability does not require prior authentication beyond the victim being a user of the affected Nextcloud instance, but it does require the victim to accept or interact with a federated share. There are no known workarounds, and the issue is fixed in richdocuments versions 6.0.0, 5.0.4, and 4.2.6. No known exploits are currently reported in the wild, but the nature of the vulnerability means that exploitation could lead to unauthorized access or manipulation of documents and collaboration sessions, potentially compromising confidentiality and integrity of data within Nextcloud Office collaboration environments.

For European organizations, the impact of this vulnerability can be significant, especially for entities relying heavily on Nextcloud for secure document collaboration, such as government agencies, educational institutions, and enterprises with sensitive intellectual property. Exploitation could allow attackers to manipulate documents or inject malicious content via federated shares, potentially leading to data leakage, unauthorized data modification, or disruption of collaborative workflows. Given Nextcloud's popularity in Europe as an open-source alternative to proprietary cloud services, organizations using vulnerable versions may face risks to confidentiality and integrity of their collaborative data. Although availability impact is limited, the trustworthiness of shared documents and collaboration sessions could be undermined, affecting operational efficiency and compliance with data protection regulations like GDPR. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits targeting this flaw.

Organizations should immediately verify the version of the richdocuments app in their Nextcloud deployments and upgrade to at least version 6.0.0, 5.0.4, or 4.2.6 as applicable. Since no workarounds exist, patching is the primary mitigation. Additionally, administrators should audit federated sharing policies and restrict federated shares to trusted domains or users where possible to reduce exposure. User education is critical: users should be trained to recognize suspicious federated share invitations and avoid interacting with unexpected or untrusted shares. Monitoring logs for unusual federated share activity can help detect attempted exploitation. Implementing network segmentation and strict access controls around Nextcloud servers can limit the impact of any compromise. Finally, organizations should review and harden their Nextcloud instance configurations, including enabling security features such as Content Security Policy (CSP) and strict origin checks if configurable, to mitigate origin validation errors.