CVE-2026-97274 in OAuth Single Sign On Plugin
Summary
by MITRE • 09/30/2026
Unauthenticated Bypass Vulnerability in OAuth Single Sign On – SSO (OAuth Client) <= 7.1.2 versions.
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Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified within the OAuth Single Sign-On implementation, specifically affecting client implementations up to version 7.1.2, represents a critical authentication bypass flaw that undermines the fundamental security guarantees of the OpenID Connect and OAuth 2.0 protocols. This issue stems from an improper validation mechanism during the authorization code exchange or token issuance phase, allowing unauthenticated actors to manipulate the flow in ways that were not anticipated by the protocol designers or the specific implementation's developers. In a standard OAuth SSO workflow, the client application redirects the user agent to the identity provider for authentication, receives an authorization code upon successful login, and then exchanges this code for access tokens using a confidential client secret. The vulnerability arises when the system fails to strictly enforce state parameter validation or improperly handles redirect URI matching during the token request phase, effectively allowing an attacker to inject malicious parameters that trick the server into issuing valid session cookies or access tokens without requiring legitimate user credentials.
From a technical perspective, this flaw typically manifests as a failure in validating the integrity of the authentication context established between the client and the identity provider. Attackers can exploit this by crafting requests where they control critical elements such as the redirect URI or state parameter, leading to session fixation or privilege escalation scenarios. By bypassing the initial authentication step, an attacker gains unauthorized access to protected resources that are normally restricted to authenticated users. This is particularly dangerous in enterprise environments where SSO serves as the primary gateway for accessing sensitive internal applications, databases, and administrative interfaces. The lack of proper input validation allows malicious actors to impersonate legitimate users or escalate their privileges by manipulating the token generation process, thereby circumventing multi-factor authentication controls if they are tied strictly to the initial login event rather than continuous verification mechanisms.
The operational impact of this vulnerability is severe, as it directly compromises the confidentiality and integrity of user sessions and organizational data. Once an attacker successfully exploits this unauthenticated bypass, they can access sensitive personal information, financial records, or proprietary business logic depending on the scope of permissions granted to the compromised account. In many cases, if the victim holds administrative privileges, the attacker may gain full control over the application infrastructure, leading to complete system compromise. Furthermore, because the attack does not require user interaction beyond clicking a malicious link in some configurations, it is highly susceptible to phishing campaigns and drive-by attacks. The absence of proper audit trails for these bypassed authentication attempts also complicates incident response efforts, as traditional security monitoring tools may not flag the anomalous token issuance behavior associated with this specific flaw.
To mitigate this risk, organizations must immediately upgrade their OAuth client implementations to a version that addresses this vulnerability, ensuring that all patches provided by the vendor are applied promptly. It is crucial to verify that the updated implementation strictly enforces state parameter validation across all endpoints involved in the authentication flow and ensures that redirect URIs are whitelisted with exact string matching rather than partial or substring comparisons. Additionally, implementing strict Content Security Policy headers and enabling comprehensive logging for token issuance events can help detect any residual exploitation attempts. Security teams should also consider adopting mutual TLS for client authentication where possible to add an additional layer of verification beyond the standard client secret mechanism. Regular penetration testing focused on OAuth flows and continuous monitoring of identity provider logs are essential practices to maintain resilience against such protocol-level attacks in modern web application architectures aligned with CWE-287 Improper Authentication standards.