CVE-2026-82287 in Rybbit
Summary
by MITRE • 08/28/2026
Rybbit before 2.7.0 contains a CORS misconfiguration vulnerability that allows attackers to bypass origin restrictions by reflecting any request origin in Access-Control-Allow-Origin responses while credentials are enabled. Attackers can issue credentialed cross-origin requests from any website to read analytics data, account information, and perform authenticated state-changing operations as the victim user.
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Analysis
by VulDB Data Team • 08/28/2026
The vulnerability identified in Rybbit versions prior to 2.7.0 represents a critical failure in Cross-Origin Resource Sharing (CORS) policy implementation, specifically categorized under CWE-942: The Permissive Wildcard Origin for Sensitive Credentials. This misconfiguration arises from an insecure coding practice where the application dynamically reflects the value of the incoming HTTP Origin header directly into the Access-Control-Allow-Origin response header without validating whether that origin is explicitly trusted or whitelisted. By employing this reflection technique, the server effectively signals to web browsers that any requesting domain is authorized to access its resources, thereby nullifying the same-origin policy protections intended to isolate sensitive data between different websites.
The severity of this flaw is significantly amplified by the concurrent enabling of credentials support on the affected endpoints. When a CORS response includes both an unrestricted or reflected origin and sets Access-Control-Allow-Credentials to true, browsers permit cross-origin requests that carry user authentication cookies, authorization headers, or other credential information. This combination creates a scenario where malicious actors can craft requests from any arbitrary website they control, which will be executed by the victim's browser with full administrative privileges associated with their active session on Rybbit. The application fails to verify if the requesting origin is legitimate before granting access and allowing credentials transmission, violating fundamental security principles regarding state management in web applications.
From an operational perspective, this vulnerability enables a range of severe attacks including Cross-Site Request Forgery (CSRF) combined with data exfiltration. An attacker can host a malicious webpage that automatically sends credentialed requests to the Rybbit application endpoints while the victim is logged in. Because the browser accepts these cross-origin responses due to the permissive CORS policy, the attacker's script gains access to sensitive server-side data such as analytics reports and personal account information. Furthermore, since authenticated state-changing operations are permitted under this misconfiguration, attackers can perform actions on behalf of the victim without their knowledge or consent, potentially leading to unauthorized modifications of user settings, deletion of records, or other destructive activities that compromise data integrity and confidentiality.
This vulnerability aligns with several entries in the MITRE ATT&CK framework, particularly T1534: Internal Spearphishing when used for initial access via social engineering links, but more directly maps to techniques involving client-side code execution and session hijacking dynamics inherent in web application attacks. It also relates to CWE-209: Generation of Error Message Containing Sensitive Information if the error responses inadvertently leak additional context during failed attempts, though the primary issue remains the improper access control logic. The flaw underscores the importance of strict origin validation mechanisms where applications must maintain a static list of allowed origins rather than relying on dynamic reflection of user-supplied input for security decisions involving sensitive credentials.
To mitigate this vulnerability and restore secure communication boundaries, it is imperative to implement an allowlist approach for CORS policies. Developers should configure the Access-Control-Allow-Origin header with specific, trusted domain names that are explicitly defined in a configuration file or database, rather than reflecting arbitrary user inputs. Additionally, if possible, applications should avoid using wildcard origins combined with credentials entirely, as this combination is inherently risky and widely discouraged by security best practices such as those outlined in OWASP guidelines for cross-origin resource sharing. Regular code audits focusing on HTTP header manipulation and automated testing of CORS configurations can help detect similar misconfigurations before they are deployed to production environments, ensuring that only authorized origins can interact with sensitive endpoints while maintaining the integrity of user sessions.