CVE-2026-78428 in NeuVector
Summary
by MITRE • 09/17/2026
For users authenticated through SAML or OpenID Connect (OIDC), this vulnerability can result in one user receiving another user's authenticated session when multiple SSO login attempts occur concurrently
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Analysis
by VulDB Data Team • 09/17/2026
The described vulnerability represents a critical authentication bypass mechanism inherent to the implementation of Single Sign-On protocols, specifically affecting systems that rely on Security Assertion Markup Language or OpenID Connect for identity management. This flaw manifests during concurrent authentication requests where the application fails to properly isolate session state between distinct user identities within the same browser context or server-side session store. When a legitimate user initiates a login process via SAML or OIDC, the service provider typically generates an intermediate session identifier while waiting for the identity provider's response. If another authenticated user from the same domain triggers a simultaneous authentication flow, race conditions in the handling of these transient states can cause the application to associate the incoming assertion with the wrong active session. Consequently, one user may inadvertently receive the authenticated session token or cookie intended for another, effectively granting unauthorized access to sensitive resources and personal data associated with the victim account without requiring valid credentials.
From a technical perspective, this issue stems from improper state management within the authentication middleware or framework. The core deficiency lies in the failure to bind the incoming identity assertion strictly to the specific transaction ID or nonce generated at the start of that particular login attempt. In many implementations, particularly those using server-side sessions with cookie-based tracking, the application may overwrite an existing session variable if it does not verify that the current request context matches the expected user state before accepting the callback from the identity provider. This lack of strict binding allows a malicious actor or even a benign concurrent action to hijack the authentication flow. The vulnerability is particularly insidious because it exploits the trust relationship between the service provider and the identity provider, assuming that any valid assertion received by the application belongs to the user currently interacting with the interface, which is not always true in high-concurrency environments.
The operational impact of this session fixation or hijacking flaw is severe, as it directly compromises the confidentiality and integrity of user accounts. An attacker who can induce concurrent login attempts could gain persistent access to another user's account by simply waiting for a race condition to occur during their own authentication process. This leads to unauthorized data exposure, potential financial fraud if payment details are stored, and manipulation of sensitive business information. Furthermore, because the session is established through legitimate protocol flows, it may bypass traditional security monitoring tools that look for anomalous login patterns or credential theft indicators. The attacker appears as a valid user with a properly issued token from the identity provider, making detection difficult without deep inspection of authentication logs and state transitions.
This vulnerability aligns closely with CWE-384, Session Fixation, specifically in scenarios where session identifiers are not sufficiently randomized or bound to unique transaction contexts during protocol handshakes. It also relates to CWE-613, Insufficient Session Expiration, as the improper association of sessions can lead to prolonged unauthorized access if the hijacked session is not invalidated promptly upon detection. In terms of offensive security frameworks, this behavior mirrors techniques found in MITRE ATT&CK under Tactic TA0004, Privilege Escalation, and more specifically aligns with methods involving Session Hijacking or Credential Stuffing where valid credentials are leveraged to assume another identity through protocol manipulation rather than brute force.
Mitigation strategies must focus on strengthening the binding between authentication requests and their corresponding responses. Developers should implement strict state parameter validation using nonces that are unique per request and bound to the specific user session before accepting any assertion from an external identity provider. It is essential to ensure that server-side sessions are isolated by generating distinct, cryptographically secure session identifiers for each concurrent login attempt rather than reusing or overwriting existing ones based on cookie presence alone. Additionally, implementing rate limiting on authentication endpoints can reduce the likelihood of race conditions being exploited in real-time attacks. Security headers such as SameSite=Strict for cookies and ensuring that tokens are transmitted only via HTTPS with proper validation further harden the implementation against interception and misuse. Regular security audits focusing on concurrent request handling and session management logic are recommended to identify similar flaws across other authentication flows within the application architecture.