CVE-2017-9286 in NextCloud
Summary
by MITRE
The packaging of NextCloud in openSUSE used /srv/www/htdocs in an unsafe manner, which could have allowed scripts running as wwwrun user to escalate privileges to root during nextcloud package upgrade.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 02/16/2023
The vulnerability identified as CVE-2017-9286 represents a critical privilege escalation flaw within the NextCloud packaging implementation on openSUSE systems. This issue stems from improper handling of directory permissions and ownership during the package installation and upgrade processes. The vulnerability specifically targets the use of /srv/www/htdocs as a staging area for web content, where the packaging mechanism failed to properly secure directory permissions that could be exploited by malicious actors.
The technical root cause of this vulnerability lies in the unsafe manipulation of file system permissions within the web server directory structure. During package upgrades, the NextCloud installation process would create or modify files within /srv/www/htdocs without properly enforcing restrictive permissions that would normally prevent the wwwrun user from gaining elevated privileges. This flaw aligns with CWE-276, which addresses improper file permissions, and represents a classic example of insecure temporary file handling that can lead to privilege escalation attacks.
The operational impact of this vulnerability is severe as it allows an attacker with access to the wwwrun user account to potentially escalate privileges to the root user during the package upgrade process. This creates a significant attack surface since web server accounts are often the first point of compromise in many security breaches. The timing aspect of this vulnerability is particularly dangerous as it only exists during package upgrades, making it difficult to detect and exploit during normal system operation. This weakness directly maps to ATT&CK technique T1068, which covers privilege escalation through exploitation of software vulnerabilities.
The exploitation of this vulnerability requires an attacker to first gain access to the wwwrun user account, typically through web application attacks such as SQL injection, cross-site scripting, or other web-based vulnerabilities. Once access is obtained, the attacker can monitor system activities during package upgrades and exploit the insecure directory handling to escalate privileges. The vulnerability demonstrates how seemingly minor packaging decisions can create significant security implications when proper privilege separation is not maintained.
Mitigation strategies for this vulnerability include implementing proper file system permission controls during package installation, ensuring that upgrade processes maintain strict ownership and permission settings, and employing more secure directory handling practices. System administrators should also implement monitoring for unauthorized package installations and upgrades, as well as ensure that web server accounts have minimal necessary permissions. The fix typically involves modifying the packaging scripts to properly secure directories and prevent the wwwrun user from gaining unintended access to system resources during upgrade operations, thereby addressing the core issue identified in CWE-276 while aligning with ATT&CK's prevention techniques for privilege escalation attacks.