CVE-2017-0888 in Server
Summary
by MITRE
Nextcloud Server before 9.0.55 and 10.0.2 suffers from a Content-Spoofing vulnerability in the "files" app. The top navigation bar displayed in the files list contained partially user-controllable input leading to a potential misrepresentation of information.
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Analysis
by VulDB Data Team • 08/25/2020
The vulnerability identified as CVE-2017-0888 represents a content-spoofing weakness within Nextcloud Server versions prior to 9.0.55 and 10.0.2, specifically affecting the files application component. This security flaw resides in the user interface presentation layer where the top navigation bar within the files list interface incorporated partially user-controllable input elements. The issue stems from insufficient sanitization of user-supplied data that flows into the navigation bar display, creating a potential vector for malicious actors to manipulate the visual representation of the application interface. The vulnerability is classified under CWE-79 as a cross-site scripting weakness, specifically manifesting as a content-spoofing attack where unauthorized modifications to the user interface can occur.
The technical implementation of this vulnerability occurs when user-generated content or parameters are directly incorporated into the navigation bar without proper input validation or sanitization processes. Attackers can exploit this by crafting malicious input that gets rendered in the navigation bar context, potentially causing the interface to display misleading information or false representations of the application state. The flaw exists because the application fails to properly escape or filter user-controllable data before it is rendered in the top navigation bar element, allowing for potential injection of HTML or JavaScript content that can alter the visual presentation of the interface. This type of vulnerability falls under the ATT&CK technique T1059 for command and scripting interpreter and T1566 for credential access through social engineering.
The operational impact of CVE-2017-0888 extends beyond simple visual manipulation as it can enable more sophisticated attacks through user interface deception. An attacker who successfully exploits this vulnerability could potentially create convincing fake navigation elements that appear to be legitimate parts of the Nextcloud interface, leading to confusion among users about their actual application state. This content-spoofing capability could facilitate phishing attempts, where users might be misled into interacting with malicious elements that appear to be legitimate interface components. The vulnerability particularly affects users who have access to the files application, as the top navigation bar is a prominent interface element that users frequently interact with during normal operations. The attack vector requires minimal privileges since it targets the presentation layer rather than underlying system functions, making it accessible to users with basic file access permissions.
Mitigation strategies for CVE-2017-0888 involve implementing proper input sanitization and output encoding measures within the Nextcloud application codebase. Organizations should immediately upgrade to Nextcloud Server versions 9.0.55 or 10.0.2 where the vulnerability has been addressed through proper input validation and sanitization of data flowing into the navigation bar display. Security measures should include comprehensive sanitization of all user-controllable input elements before rendering them in interface components, particularly in navigation bars and other prominent UI elements. Additionally, implementing Content Security Policy headers can provide additional defense-in-depth against potential exploitation attempts. The fix typically involves ensuring that user-supplied data is properly escaped or filtered before being incorporated into HTML rendering contexts, preventing malicious input from being interpreted as executable content within the navigation bar component. Organizations should also conduct regular security assessments of their Nextcloud installations to identify similar vulnerabilities in other application components that might present similar content-spoofing risks.