CVE-2023-32319 in Server
Summary
by MITRE • 05/27/2023
Nextcloud server is an open source personal cloud implementation. Missing brute-force protection on the WebDAV endpoints via the basic auth header allowed to brute-force user credentials when the provided user name was not an email address. Users from version 24.0.0 onward are affected. This issue has been addressed in releases 24.0.11, 25.0.5 and 26.0.0. Users are advised to upgrade. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 06/21/2023
The vulnerability identified as CVE-2023-32319 represents a critical authentication weakness in Nextcloud server implementations that affects versions 24.0.0 and later. This flaw specifically targets the WebDAV endpoints within the Nextcloud platform, which serve as core components for file synchronization and cloud storage operations. The vulnerability manifests when the system employs basic authentication headers for user verification, creating an exploitable pathway for malicious actors to systematically test user credentials through automated brute-force attacks.
The technical flaw stems from the absence of proper rate-limiting and account lockout mechanisms specifically designed to protect against credential guessing attacks on WebDAV interfaces. When user names are provided as usernames rather than email addresses, the authentication system fails to implement necessary protective measures that would typically be enforced for email-based authentication. This creates a significant security gap where attackers can exploit the system's lack of defensive controls to conduct repeated authentication attempts without triggering protective mechanisms. The vulnerability operates at the application layer and specifically targets the authentication process within Nextcloud's WebDAV implementation, making it particularly dangerous as it directly undermines the fundamental security of user access controls.
The operational impact of this vulnerability extends beyond simple credential theft, as successful exploitation could lead to unauthorized access to sensitive user data, potential data exfiltration, and compromise of user accounts within the Nextcloud environment. Attackers could systematically target user credentials through automated tools, potentially gaining access to personal files, shared documents, and other sensitive information stored within the cloud platform. The vulnerability affects all Nextcloud installations running version 24.0.0 or higher, making it widespread across many production environments that rely on this open-source cloud solution for personal and organizational data storage. Organizations using Nextcloud for file synchronization and collaboration services face significant risk if they fail to address this vulnerability promptly.
Security researchers have identified this issue as a failure to implement proper authentication controls that align with established security best practices and standards such as those outlined in CWE-307, which addresses improper restriction of excessive authentication attempts. The vulnerability also maps to ATT&CK technique T1110.003, which covers the use of credential stuffing and brute force attacks against web applications. The affected Nextcloud versions demonstrate a lack of robust account lockout mechanisms and rate-limiting controls that are essential for preventing automated credential testing attacks. Organizations should immediately implement the recommended upgrades to versions 24.0.11, 25.0.5, or 26.0.0 to address this vulnerability. The absence of known workarounds means that organizations cannot rely on temporary mitigations and must prioritize the upgrade process to ensure their Nextcloud installations remain secure against credential brute-force attacks. This vulnerability underscores the importance of implementing comprehensive authentication controls and highlights the risks associated with inadequate protection mechanisms in web-based cloud storage platforms.