CVE-2025-63386 identifies a critical CORS misconfiguration vulnerability in Dify version 1.9.1, specifically within the /console/api/setup endpoint. The vulnerability arises because the endpoint reflects the Origin header value from incoming requests without validation and sets the Access-Control-Allow-Credentials header to true. This combination allows any external domain to bypass same-origin policy restrictions and make authenticated requests to the vulnerable endpoint using the victim's credentials or session. Essentially, an attacker can craft a malicious website that, when visited by an authenticated user, can perform unauthorized actions or access sensitive data through the victim's browser. The lack of a CVSS score suggests this is a newly published vulnerability with limited public analysis. However, the technical details indicate a high risk because the vulnerability directly undermines the browser's security model, enabling cross-origin attacks that can compromise confidentiality and integrity. No authentication bypass is required beyond the victim being authenticated, and no user interaction beyond visiting a malicious site is necessary. The vulnerability affects all deployments of Dify v1.9.1 that have not patched or mitigated the issue. No known exploits have been reported yet, but the nature of the flaw makes exploitation feasible and potentially widespread once weaponized.

For European organizations using Dify v1.9.1, this vulnerability poses a significant risk to the confidentiality and integrity of sensitive data and operations. Attackers can leverage the misconfigured CORS policy to perform unauthorized actions on behalf of authenticated users, potentially leading to data leakage, unauthorized configuration changes, or privilege escalation within the affected application. This can disrupt business processes, lead to compliance violations (e.g., GDPR breaches due to data exposure), and damage organizational reputation. The vulnerability's exploitation requires only that the victim visit a malicious website, increasing the attack surface through phishing or drive-by attacks. Organizations relying on Dify for critical internal or customer-facing services may face operational disruptions and increased risk of targeted attacks. The absence of known exploits currently provides a window for proactive mitigation, but the vulnerability's characteristics suggest it could be rapidly exploited once publicly disclosed.

Organizations should immediately audit their Dify installations, focusing on version 1.9.1 and the /console/api/setup endpoint. Specific mitigation steps include: 1) Restrict the Access-Control-Allow-Origin header to a whitelist of trusted domains rather than reflecting the Origin header dynamically. 2) Disable Access-Control-Allow-Credentials unless absolutely necessary, and if enabled, ensure strict origin validation. 3) Implement server-side validation to reject requests with suspicious or unauthorized Origin headers. 4) Monitor and log CORS-related requests to detect abnormal patterns indicative of exploitation attempts. 5) Apply any available patches or updates from Dify vendors as soon as they are released. 6) Educate users about phishing risks to reduce the likelihood of visiting malicious sites that could exploit this vulnerability. 7) Consider deploying Web Application Firewalls (WAFs) with rules to detect and block suspicious cross-origin requests targeting the vulnerable endpoint. These measures go beyond generic advice by focusing on precise CORS policy hardening and proactive monitoring tailored to this vulnerability.