CVE-2026-85161 in AVideo
Summary
by MITRE • 09/03/2026
AVideo through commit c91b5975d contains a cross-site request forgery vulnerability in removePoster.php that lacks forbidIfNotPost or forbidIfInvalidToken checks. Attackers can craft malicious image tags to delete authenticated victims' live poster and thumbnail files via GET requests.
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Analysis
by VulDB Data Team • 09/03/2026
The identified security flaw resides within the AVideo content management platform, specifically affecting the removePoster.php module prior to commit c91b5975d. This vulnerability is classified as a Cross-Site Request Forgery (CSRF), which exploits the trust that a web application has in an authenticated user's browser. In this specific instance, the endpoint responsible for removing live poster and thumbnail files fails to implement critical anti-CSRF protections. The absence of checks such as forbidIfNotPost or forbidIfInvalidToken means that the server does not verify whether incoming requests originate from legitimate, intended sources within the application itself. Instead, it accepts state-changing actions triggered by simple GET requests without validating a unique, secret token associated with the user's session. This architectural oversight allows an attacker to bypass standard security controls designed to prevent unauthorized command execution on behalf of authenticated users.
From a technical perspective, the vulnerability leverages the fact that many web browsers automatically include cookies and other authentication credentials in HTTP requests made by embedded resources like images or scripts. An attacker can construct a malicious webpage containing an HTML image tag with its source attribute pointing directly to the vulnerable removePoster.php endpoint on the target AVideo server. When an authenticated victim visits this malicious page, their browser will silently send a GET request to delete specific poster and thumbnail files associated with that user's account or content. Because the application does not require a POST method nor validate a CSRF token, it processes the deletion command as if it were initiated by the legitimate user. This mechanism effectively allows an unauthenticated remote attacker to force state changes on behalf of any authenticated victim without their knowledge or consent.
The operational impact of this vulnerability is significant for users relying on AVideo for hosting and managing video content with associated visual assets like posters and thumbnails. The successful exploitation leads to unauthorized data modification, specifically the deletion of critical media files that are essential for user experience and content presentation. This results in a denial of service for those specific assets, potentially disrupting streaming services or requiring manual restoration from backups if available. Beyond immediate availability issues, this flaw undermines the integrity of the application's file management system. It demonstrates a failure to enforce proper access controls on state-changing operations, which can erode user trust and expose organizations to further risks if similar patterns exist in other parts of the platform that handle sensitive data or configurations.
This vulnerability aligns with CWE-352, Cross-Site Request Forgery (CSRF), as it involves forcing an authenticated user to execute unwanted actions on a web application without their consent. Furthermore, from a tactical perspective within the MITRE ATT&CK framework, this exploit maps to T1076, which describes Direct Remote Execution via Web Protocols or more broadly under T1498, Network Denial of Service if the deletion causes service disruption. To mitigate this risk, developers must implement robust anti-CSRF measures across all state-changing endpoints. This includes requiring a unique, unpredictable CSRF token that is validated on every POST request and ensuring that sensitive operations are not performed via GET requests which can be triggered by simple image tags or hyperlinks. Additionally, implementing the SameSite cookie attribute to strict mode can provide an additional layer of defense by preventing browsers from sending cookies in cross-site contexts, thereby neutralizing many CSRF attack vectors at the browser level.