CVE-2026-3303 in Concert
Summary
by MITRE • 10/19/2026
IBM Concert 1.0 through 3.0.0 uses cross-origin resource sharing (CORS) which could allow an attacker to carry out privileged actions as the domain name is not being limited to only trusted domains.
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Analysis
by VulDB Data Team • 10/19/2026
The vulnerability identified in IBM Concert versions 1.0 through 3.0.0 stems from a misconfiguration of Cross-Origin Resource Sharing policies, specifically categorized under CWE-942 Improper Restriction of Excessive Authentication Requests or more accurately CWE-942 Incorrect Origin Header Validation when considering the context of CORS bypasses that lead to unauthorized access. In modern web architectures, browsers enforce same-origin security policies by default, preventing scripts from one origin from accessing resources on another unless explicitly permitted via headers such as Access-Control-Allow-Origin. IBM Concert relies heavily on these mechanisms for its internal communication and API interactions between different components or services within the application ecosystem. However, the implementation in this version range fails to strictly validate the Origin header against a whitelist of trusted domains. This oversight allows any arbitrary domain to initiate requests that are treated as legitimate by the server-side logic handling CORS preflight responses or actual data retrieval operations.
From an operational perspective, this flaw enables attackers to perform Cross-Site Request Forgery attacks with elevated privileges because the browser will include credentials such as session cookies in cross-origin requests if Access-Control-Allow-Credentials is set to true and the origin check is bypassed due to overly permissive wildcard configurations or missing validation logic. An attacker can craft a malicious webpage that, when visited by an authenticated user of IBM Concert, triggers HTTP requests to vulnerable endpoints within the application. Since the server does not verify whether the request originated from a trusted source, it processes these actions as if they were initiated directly by the legitimate client. This effectively allows the attacker to execute privileged operations on behalf of the victim without their knowledge or consent, leveraging the user's active session and associated permissions.
The impact of this vulnerability is significant in environments where IBM Concert manages sensitive data or critical infrastructure configurations. Attackers can potentially read confidential information exposed through API endpoints that are protected by authentication but not by origin restrictions. Furthermore, they may modify settings, delete resources, or execute administrative commands depending on the specific privileges held by the targeted user account. This aligns with MITRE ATT&CK technique T1534, which covers Internal Spearphishing and related social engineering vectors where web-based attacks are used to compromise internal systems. It also relates to T1078 Valid Accounts, as the exploitation relies on hijacking or leveraging valid session tokens from authenticated users within the organization's network perimeter.
Mitigation strategies must focus on implementing strict origin validation at both the application and infrastructure levels. Developers should configure Access-Control-Allow-Origin headers to explicitly list only those domains that are authorized to interact with IBM Concert APIs, avoiding the use of wildcard characters such as asterisks which permit access from any source. Additionally, enabling preflight request handling for non-simple methods ensures that browsers verify permissions before sending state-changing requests like POST or PUT. Network-level controls can also be employed by configuring reverse proxies or web application firewalls to inspect and filter Origin headers based on a predefined allowlist of trusted internal domains. Regular security audits and penetration testing should be conducted to ensure that CORS policies remain aligned with the principle of least privilege, thereby preventing unauthorized cross-origin interactions from compromising system integrity.