CVE-2017-16636 in Bludit
Summary
by MITRE
In Bludit v1.5.2 and v2.0.1, an XSS vulnerability is located in the new page, new category, and edit post function body message context. Remote attackers are able to bypass the basic editor validation to trigger cross site scripting. The XSS is persistent and the request method to inject via editor is GET. To save the editor context, the followup POST method request must be processed to perform the attack via the application side. The basic validation of the editor does not allow injecting script codes and blocks the context. Attackers can inject the code by using an editor tag that is not recognized by the basic validation. Thus allows a restricted user account to inject malicious script code to perform a persistent attack against higher privilege web-application user accounts.
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Analysis
by VulDB Data Team • 12/04/2019
The vulnerability described in CVE-2017-16636 represents a critical cross-site scripting flaw within Bludit content management systems version 1.5.2 and 2.0.1. This vulnerability specifically targets the application's rich text editor functionality, affecting three primary administrative operations: creating new pages, creating new categories, and editing existing posts. The security flaw stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied content before processing it within the application's editor context.
The technical implementation of this vulnerability exploits a fundamental weakness in the application's validation architecture where the system employs basic editor validation that appears to block script injection attempts. However, attackers can bypass these protections by utilizing unrecognized editor tags that are not properly filtered or validated by the application's security mechanisms. This allows malicious actors to inject script code that gets stored in the application's database and subsequently executed whenever affected pages are rendered. The vulnerability requires a two-step process for exploitation where initial GET requests containing malicious payloads must be followed by POST requests to actually persist the malicious content within the application's data store.
The operational impact of this vulnerability is particularly severe as it enables persistent cross-site scripting attacks that can target users with higher privilege levels within the application. The vulnerability specifically affects restricted user accounts that should not have the ability to execute arbitrary code, yet through this flaw they can inject malicious scripts that will execute against other users, potentially including administrators or editors with elevated permissions. This creates a significant privilege escalation vector where low-privilege users can compromise the entire application environment. The persistent nature of the vulnerability means that once successfully exploited, the malicious scripts will continue to execute whenever affected content is accessed, making it particularly dangerous for ongoing attacks.
From a cybersecurity perspective, this vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications. The attack pattern follows typical ATT&CK techniques for server-side web application attacks where initial access is gained through application-level vulnerabilities rather than client-side exploitation. The vulnerability's persistence mechanism and the requirement for both GET and POST operations to complete the attack sequence demonstrates a sophisticated approach to bypassing traditional input validation controls. Organizations using affected Bludit versions should immediately implement mitigation strategies including comprehensive input sanitization, enhanced validation of editor tags, and proper content encoding to prevent script execution. Additionally, implementing proper access controls and privilege separation would significantly reduce the impact of this vulnerability by limiting the ability of restricted users to affect system-wide security. The vulnerability underscores the critical importance of robust input validation and the potential for seemingly minor validation bypasses to create significant security risks in web applications.