CVE-2026-109461 in Authentication Library
Summary
by MITRE • 10/16/2026
Origin validation error in Microsoft Authentication Library (MSAL) for Node.js allows an unauthorized attacker to disclose information over a network.
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Analysis
by VulDB Data Team • 10/16/2026
The vulnerability identified within the Microsoft Authentication Library for Node.js represents a critical failure in origin validation mechanisms, specifically affecting how the library handles cross-origin resource sharing and token exchange processes. This flaw stems from insufficient verification of the request source during authentication flows, allowing an attacker to manipulate or spoof the expected origins that are typically validated by security policies such as Content Security Policy headers or same-origin policy implementations. In a standard secure configuration, MSAL ensures that tokens and sensitive session data are only processed when requests originate from trusted domains explicitly whitelisted in the application's configuration. However, due to this validation error, the library fails to strictly enforce these boundaries under certain conditions, effectively bypassing the intended isolation between different web origins.
From a technical perspective, the core issue lies in the logic that determines whether an incoming request is legitimate based on its origin header or referrer information. When this check is flawed, it creates a pathway for unauthorized actors to inject malicious payloads or intercept sensitive authentication data. The attacker can exploit this by crafting requests that appear to originate from trusted sources while actually being routed through controlled endpoints under their jurisdiction. This misconfiguration allows the library to accept and process tokens or session cookies intended for other contexts, leading to a breakdown in the trust model established by OAuth 2.0 and OpenID Connect protocols which rely heavily on strict origin binding to prevent identity theft and session hijacking attacks.
The operational impact of this vulnerability is severe, primarily centering around information disclosure and potential account takeover scenarios. An unauthorized attacker leveraging this flaw can disclose sensitive user information such as access tokens, refresh tokens, or personal identifiable data contained within the authentication response. This exposure compromises the confidentiality integrity of the application's users and may allow further lateral movement within an enterprise environment if those tokens are used to access downstream services like Microsoft Graph APIs or other integrated SaaS applications. The ability to disclose this information over a network means that remote exploitation is feasible without requiring physical access or prior local privileges, significantly expanding the attack surface available to malicious actors targeting organizations using Node.js-based authentication systems powered by MSAL.
This vulnerability aligns with CWE-346 which describes Origin Validation Errors, indicating a failure in verifying the source of data before processing it securely. It also maps closely to MITRE ATT&CK techniques related to Credential Access and Defense Evasion, specifically where attackers exploit misconfigurations or logic flaws to bypass authentication controls. To mitigate this risk, organizations must immediately update their Microsoft Authentication Library dependencies to versions that include patches for origin validation checks. Additionally, developers should implement strict Content Security Policy headers with appropriate frame-ancestors and form-action directives to add a layer of defense-in-depth. It is also recommended to review application configurations to ensure that only explicitly trusted origins are permitted in the MSAL configuration object, thereby minimizing the risk of cross-origin data leakage even if similar vulnerabilities arise in future library updates.