CVE-2021-32652 in NextCloud Mail
Summary
by MITRE • 06/02/2021
Nextcloud Mail is a mail app for the Nextcloud platform. A missing permission check in Nextcloud Mail before 1.4.3 and 1.8.2 allows another authenticated users to access mail metadata of other users. Versions 1.4.3 and 1.8.2 contain patches for this vulnerability; no workarounds other than the patches are known to exist.
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Analysis
by VulDB Data Team • 11/20/2024
The vulnerability identified as CVE-2021-32652 represents a critical authorization flaw within the Nextcloud Mail application that affects versions prior to 1.4.3 and 1.8.2. This issue stems from a missing permission check that fundamentally undermines the security model of the mail application, creating a scenario where authenticated users can bypass normal access controls to obtain sensitive metadata from other users' email accounts. The vulnerability specifically impacts the Nextcloud platform's email functionality, which serves as a core collaborative tool for organizations relying on Nextcloud for their file sharing and communication needs.
The technical flaw manifests as an insufficient validation mechanism that fails to properly verify user permissions when accessing mail metadata. This weakness allows authenticated attackers to exploit the application's API endpoints and retrieve information such as email subject lines, sender addresses, recipient details, timestamps, and other metadata without proper authorization. The vulnerability operates at the application logic level, where the system should enforce strict access controls between user accounts but instead permits cross-user data access. This type of flaw falls under the CWE-284 category of Improper Access Control, specifically addressing inadequate permission checking mechanisms that allow unauthorized access to resources.
The operational impact of this vulnerability extends beyond simple data exposure, as the metadata obtained through this flaw can provide attackers with significant reconnaissance information about user communication patterns, organizational structures, and potential security targets. Attackers can leverage this information to craft more sophisticated social engineering attacks, identify high-value targets within an organization, or map out communication networks that may reveal sensitive business relationships. The vulnerability affects the confidentiality aspect of the CIA security triad, as it allows unauthorized information disclosure that could lead to further compromise of user accounts or organizational security. Organizations using Nextcloud Mail without the patched versions face potential exposure of sensitive email metadata that could be used for targeted attacks or information gathering.
Mitigation of this vulnerability requires immediate deployment of the security patches released in Nextcloud Mail versions 1.4.3 and 1.8.2, as no effective workarounds exist for this specific authorization flaw. System administrators should prioritize updating their Nextcloud installations to ensure all users benefit from the implemented permission checks. The fix addresses the root cause by enforcing proper access control mechanisms that validate user permissions before allowing access to mail metadata, aligning with the principle of least privilege. Organizations should also conduct security reviews of their Nextcloud implementations to verify that all components have been updated and that no other similar authorization flaws exist within their Nextcloud ecosystem. This vulnerability demonstrates the critical importance of proper permission validation in collaborative platforms where multiple users share common infrastructure and resources.