CVE-2020-5222 in Opencast
Summary
by MITRE
Opencast before 7.6 and 8.1 enables a remember-me cookie based on a hash created from the username, password, and an additional system key. This means that an attacker getting access to a remember-me token for one server can get access to all servers which allow log-in using the same credentials without ever needing the credentials. This problem is fixed in Opencast 7.6 and Opencast 8.1
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Analysis
by VulDB Data Team • 03/27/2024
The vulnerability described in CVE-2020-5222 represents a critical security flaw in Opencast versions prior to 7.6 and 8.1, specifically within the remember-me authentication mechanism. This issue stems from a cryptographic weakness in how session tokens are generated and validated across multiple server instances. The vulnerability exposes a fundamental design flaw in the authentication system where the remember-me cookie is constructed using a hash function that incorporates the username, password, and a system key. This approach fundamentally undermines the security model by creating a deterministic relationship between authentication credentials and session tokens that persists across different server instances.
The technical implementation of this vulnerability creates a scenario where an attacker who compromises a single remember-me token gains the ability to authenticate across multiple Opencast servers that share the same credential set. This occurs because the hash algorithm used does not properly incorporate randomization or unique server-specific components, making the token generation predictable and reusable. The system key, which should provide server-specific entropy, is insufficiently utilized or shared across environments, creating a single point of failure that allows lateral movement without credential exposure. This flaw directly relates to CWE-326, which addresses insufficient key size or weak cryptographic algorithms, and CWE-327, which covers the use of weak or broken cryptographic algorithms.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it enables attackers to maintain persistent access across multiple server instances without ever needing to know or guess the actual credentials. This creates a significant risk for organizations using Opencast in distributed environments where multiple servers might share authentication backends or where credential reuse occurs. The vulnerability essentially eliminates the need for credential compromise, as the remember-me token serves as a direct authentication bypass mechanism. Attackers can leverage this weakness to conduct extended surveillance, data exfiltration, or system manipulation across multiple servers, making it particularly dangerous for environments where Opencast is used for sensitive content management or educational video distribution.
Organizations should immediately implement mitigations including upgrading to Opencast versions 7.6 or 8.1 where this vulnerability has been addressed. The fix typically involves implementing proper randomization in token generation, ensuring that each server instance uses unique cryptographic parameters, and implementing server-specific key derivation functions. Additional protective measures include disabling remember-me functionality where possible, implementing stricter session management policies, and monitoring for unusual authentication patterns. Security teams should also conduct comprehensive audits of all Opencast installations to identify and remediate any instances running vulnerable versions, while ensuring that proper key management practices are implemented across all server environments to prevent similar issues in the future. This vulnerability demonstrates the critical importance of proper cryptographic implementation and the dangers of shared secrets in distributed authentication systems, aligning with ATT&CK technique T1566 for credential access and T1078 for valid accounts.