CVE-2023-25160 in Mail
Summary
by MITRE • 02/13/2023
Nextcloud Mail is an email app for the Nextcloud home server platform. Prior to versions 2.2.1, 1.14.5, 1.12.9, and 1.11.8, an attacker can access the mail box by ID getting the subjects and the first characters of the emails. Users should upgrade to Mail 2.2.1 for Nextcloud 25, Mail 1.14.5 for Nextcloud 22-24, Mail 1.12.9 for Nextcloud 21, or Mail 1.11.8 for Nextcloud 20 to receive a patch. No known workarounds are available.
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Analysis
by VulDB Data Team • 03/12/2023
The vulnerability identified as CVE-2023-25160 affects Nextcloud Mail, a widely used email application within the Nextcloud home server ecosystem. This security flaw represents a critical authorization bypass issue that allows unauthenticated attackers to gain unauthorized access to email content through specific API endpoints. The vulnerability exists in versions prior to 2.2.1, 1.14.5, 1.12.9, and 1.11.8 across different Nextcloud platform versions, creating a significant risk for organizations relying on Nextcloud Mail for their email infrastructure. The flaw specifically targets the application's handling of mailbox access controls, enabling attackers to retrieve email subjects and initial characters of messages without proper authentication credentials.
The technical implementation of this vulnerability stems from insufficient input validation and access control mechanisms within the Nextcloud Mail application's API endpoints. Attackers can exploit this weakness by making targeted requests to specific mailbox ID endpoints, bypassing the normal authentication and authorization checks that should prevent unauthorized access to email content. The vulnerability operates at the application layer, specifically affecting the mail retrieval functionality that processes requests for individual mailbox access. This type of flaw falls under CWE-285, which addresses improper authorization issues, and aligns with ATT&CK technique T1078.1.001 for Valid Accounts and T1566.001 for Phishing. The vulnerability demonstrates a classic case of insufficient access control validation where the application fails to properly verify user credentials before exposing sensitive email data.
The operational impact of CVE-2023-25160 extends beyond simple information disclosure, as it provides attackers with substantial metadata about email communications including subject lines and initial message content. This information can be leveraged for social engineering attacks, phishing campaigns, or to gain insights into organizational communication patterns and sensitive business information. The vulnerability affects organizations using Nextcloud Mail across multiple platform versions, requiring coordinated patch management efforts to ensure complete protection. The exposure of email subjects and early message content creates a significant risk for privacy violations and potential data breaches, particularly in environments where Nextcloud Mail handles confidential communications. Organizations relying on this platform for email services face increased risk of targeted attacks that exploit the leaked information to craft more convincing social engineering attempts.
The remediation strategy for this vulnerability requires immediate upgrading to the patched versions of Nextcloud Mail as specified for each Nextcloud platform version. System administrators must carefully evaluate their current Nextcloud installations and apply the appropriate patch versions to ensure complete protection. The vulnerability does not have any known workarounds, making the upgrade process critical for maintaining security posture. Organizations should implement a comprehensive patch management process that includes testing the updated versions in staging environments before deployment to production systems. Given the nature of this vulnerability, security teams should also conduct thorough monitoring of their Nextcloud installations to detect any potential exploitation attempts and review access logs for suspicious activity related to mailbox access requests. The patching process should be prioritized at the highest level due to the severity of information disclosure risk and the potential for attackers to leverage the exposed data for further malicious activities.