CVE-2017-8298 in Canvas
Summary
by MITRE
cnvs.io Canvas 3.3.0 has XSS in the title and content fields of a "Posts > Add New" action, and during creation of new tags and users.
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Analysis
by VulDB Data Team • 12/02/2022
The vulnerability identified as CVE-2017-8298 affects cnvs.io Canvas version 3.3.0 and represents a cross-site scripting flaw that manifests in multiple administrative interfaces. This security weakness allows attackers to inject malicious scripts into the application's title and content fields when creating new posts through the "Posts > Add New" action. The vulnerability extends beyond simple post creation to encompass the tag and user creation processes, indicating a broader input sanitization failure within the application's administrative components.
The technical implementation of this vulnerability stems from insufficient validation and sanitization of user inputs in the web application's backend processing. When administrators or users submit content through the specified interfaces, the application fails to properly escape or filter special characters that could be interpreted as executable script code by web browsers. This flaw falls under the CWE-79 category of Cross-Site Scripting, specifically representing a stored XSS vulnerability where malicious payloads persist in the application's database and execute whenever the affected content is rendered to other users. The vulnerability exists in the application's user input handling mechanism, where data validation occurs too late in the processing pipeline or not at all in critical administrative functions.
The operational impact of this vulnerability is significant as it enables attackers to execute arbitrary JavaScript code within the context of authenticated users' browsers. An attacker could potentially steal session cookies, perform unauthorized actions on behalf of victims, redirect users to malicious sites, or even escalate privileges if the affected application has administrative capabilities. The vulnerability affects both regular users and administrators, as the XSS can be triggered through any of the affected input fields during post, tag, or user creation processes. This creates a persistent threat vector that could be exploited repeatedly by attackers who gain access to the application's administrative interface or by targeting less privileged users who might inadvertently trigger the malicious script execution.
Mitigation strategies for CVE-2017-8298 should focus on implementing comprehensive input validation and output encoding mechanisms throughout the application's data handling pipeline. The most effective approach involves applying strict sanitization to all user inputs before they are processed or stored in the database, utilizing established libraries or frameworks designed for HTML and script sanitization. Organizations should implement Content Security Policy headers to limit script execution capabilities and employ proper output encoding when rendering user-supplied content to prevent script interpretation. Regular security audits and penetration testing should be conducted to identify similar input validation weaknesses across the application. Additionally, upgrading to a patched version of cnvs.io Canvas or implementing web application firewalls that can detect and block malicious script patterns would provide immediate protection against exploitation attempts. The vulnerability aligns with ATT&CK technique T1213 which involves data from information repositories and demonstrates the importance of proper input validation in preventing persistent security flaws within web applications.