CVE-2017-0892 in Server
Summary
by MITRE
Nextcloud Server before 11.0.3 is vulnerable to an improper session handling allowed an application specific password without permission to the files access to the users file.
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Analysis
by VulDB Data Team • 09/24/2020
The vulnerability identified as CVE-2017-0892 affects Nextcloud Server versions prior to 11.0.3 and represents a critical session management flaw that undermines the security of user file access controls. This weakness stems from improper session handling mechanisms that fail to adequately validate authentication tokens when users attempt to access files through application-specific passwords. The vulnerability allows authenticated attackers to bypass normal file access restrictions and gain unauthorized access to user files through these specially crafted authentication mechanisms.
The technical root cause of this vulnerability lies in the insufficient validation of session tokens and authentication contexts within Nextcloud's file access subsystem. When users generate application-specific passwords for third-party applications or services, the system should enforce strict access controls that align with the original user permissions and session context. However, the flawed implementation fails to properly verify that the application-specific password is being used within the appropriate session context, allowing attackers to exploit this gap and access files they should not be authorized to view. This issue falls under the category of CWE-287 Improper Authentication, specifically addressing weaknesses in session management and credential validation processes.
The operational impact of this vulnerability extends beyond simple unauthorized file access, as it creates potential for data exfiltration and privacy breaches across affected Nextcloud deployments. Attackers could leverage this flaw to access sensitive user data, including documents, photos, and other personal files stored within the cloud environment. The vulnerability affects organizations that rely on Nextcloud for collaborative file sharing and storage, potentially exposing confidential information to unauthorized parties. The risk is particularly severe in enterprise environments where Nextcloud serves as a primary file storage solution for business-critical data, as it could lead to significant compliance violations and regulatory penalties.
Mitigation strategies for CVE-2017-0892 require immediate deployment of Nextcloud Server version 11.0.3 or later, which contains the necessary patches to address the session handling flaws. Organizations should also implement additional security controls including regular monitoring of authentication logs for suspicious activity, enforcing multi-factor authentication for sensitive accounts, and reviewing application-specific password permissions regularly. Security teams should conduct comprehensive vulnerability assessments to identify any other potential session management weaknesses within their Nextcloud deployments and related applications. The ATT&CK framework categorizes this vulnerability under T1078 Valid Accounts and T1566 Phishing, as it exploits legitimate authentication mechanisms to gain unauthorized access. Organizations should also consider implementing network segmentation and access control measures to limit the potential impact of such vulnerabilities and establish robust incident response procedures to quickly address any exploitation attempts.