CVE-2020-8296 in Nextcloud Server
Summary
by MITRE • 03/04/2021
Nextcloud Server prior to 20.0.0 stores passwords in a recoverable format even when external storage is not configured.
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Analysis
by VulDB Data Team • 03/14/2021
The vulnerability identified as CVE-2020-8296 affects Nextcloud Server versions prior to 20.0.0 and represents a critical security flaw in how the platform handles password storage for external storage connections. This issue manifests when external storage is not configured but the system still maintains passwords in a recoverable format, creating an unnecessary security risk that could be exploited by malicious actors with access to the system. The flaw directly violates fundamental security principles by storing authentication credentials in a manner that allows for easy recovery and potential misuse.
The technical root cause of this vulnerability lies in Nextcloud's improper handling of password encryption mechanisms within its storage configuration system. When external storage is not actively configured, the application should not retain password information in any form, yet the vulnerable versions maintain these credentials in a recoverable state. This behavior creates a persistent security exposure where password hashes or plain text credentials may be accessible through various attack vectors including direct file system access, database queries, or through compromised user sessions. The vulnerability essentially represents a failure in proper credential management and access control implementation.
The operational impact of CVE-2020-8296 extends beyond simple credential exposure to encompass broader system compromise risks. Attackers who gain access to a vulnerable Nextcloud instance can potentially recover passwords for external storage systems, including cloud services, network drives, or other connected resources that may contain sensitive organizational data. This vulnerability can be particularly dangerous in enterprise environments where Nextcloud serves as a central collaboration platform with access to critical business data. The risk is amplified when considering that these stored passwords may grant unauthorized access to additional systems and resources beyond the immediate Nextcloud environment, creating potential lateral movement opportunities for attackers.
Organizations should immediately implement mitigations including upgrading to Nextcloud Server version 20.0.0 or later, which contains the necessary patches to address this vulnerability. System administrators must conduct thorough audits of existing Nextcloud installations to identify and remediate vulnerable systems, particularly focusing on configurations where external storage was not actively used but credentials may still be present. Additional protective measures include implementing strict access controls for Nextcloud system files, monitoring for unauthorized access attempts, and ensuring that all external storage configurations follow secure practices including the use of dedicated service accounts with minimal required permissions. This vulnerability aligns with CWE-312 (Sensitive Data Exposure) and may be exploited through techniques categorized under ATT&CK tactic TA0006 (Credential Access) and technique T1552 (Unsecured Credentials).