CVE-2026-70482 in Open WebUI
Summary
by MITRE • 08/04/2026
Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.8.0 until 0.11.0, when ENABLE_OAUTH_TOKEN_EXCHANGE=True, /oauth/{provider}/token/exchange accepts a raw provider access token and validates it by calling the provider userinfo endpoint without confirming which OAuth client the token was issued to. Anyone holding an access token minted for any client registered with the same provider could exchange it for an Open WebUI session as that token user, including applications the operator does not control and has never authorized. This issue is fixed in 0.11.0.
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Analysis
by VulDB Data Team • 08/04/2026
This vulnerability exists within the Open WebUI platform version range from 0.8.0 through 0.11.0, specifically when the ENABLE_OAUTH_TOKEN_EXCHANGE feature is activated. The flaw stems from improper validation of OAuth access tokens during the token exchange process, creating a critical security weakness that undermines the authentication system's integrity. When ENABLE_OAUTH_TOKEN_EXCHANGE=True, the platform accepts raw provider access tokens through the /oauth/{provider}/token/exchange endpoint and validates them by calling the provider's userinfo endpoint without verifying which specific OAuth client the token was originally issued to.
The technical implementation of this vulnerability allows for cross-client token forgery attacks where an attacker can leverage any valid access token from a provider that has been registered with Open WebUI. The system fails to enforce client-specific token validation, meaning that if a token was issued to one application but is presented to the exchange endpoint, the platform will accept it and create a session as if the legitimate client had authenticated. This represents a fundamental breakdown in OAuth security principles where the authorization server should verify that tokens are being used by the correct client application.
The operational impact of this vulnerability is severe as it enables unauthorized access to Open WebUI sessions using tokens from any registered client within the same OAuth provider. An attacker could potentially use tokens from applications they do not control or have never authorized, effectively bypassing the intended authorization boundaries and gaining unauthorized access to user sessions. This creates a significant risk for operators who rely on Open WebUI for secure access management, as their platform becomes vulnerable to token-based attacks that can be executed without proper authorization.
This vulnerability aligns with CWE-287 which addresses improper authentication issues in software systems, specifically targeting the failure to properly validate authentication tokens against their intended clients. The flaw also maps to ATT&CK technique T1566 which covers credential harvesting through phishing and social engineering, as it essentially allows for unauthorized credential reuse through token exchange mechanisms. The security weakness demonstrates a classic case of insufficient client validation where the system assumes all valid tokens from a provider are equally trustworthy regardless of their original issuing client.
The fix implemented in version 0.11.0 addresses this by introducing proper client validation during the OAuth token exchange process, ensuring that access tokens can only be exchanged for sessions when they were originally issued to the same client application attempting the exchange. This remediation enforces proper OAuth security boundaries and prevents cross-client token forgery attacks that could otherwise allow unauthorized users to impersonate legitimate clients within the Open WebUI platform.
Organizations using Open WebUI should immediately upgrade to version 0.11.0 or later to mitigate this vulnerability, while also reviewing their existing OAuth configurations to ensure that client registration practices follow security best practices. The fix demonstrates the critical importance of proper token validation and client authentication in multi-client OAuth environments where unauthorized access could result in significant security breaches across multiple applications sharing the same authentication provider infrastructure.
Security teams should monitor for potential exploitation attempts using this vulnerability during the upgrade process, as attackers may attempt to leverage this weakness before organizations implement the necessary patches. The implementation of proper client validation represents a fundamental improvement in OAuth security posture that aligns with industry standards for secure token management and prevents unauthorized access through compromised or misused authentication tokens within the Open WebUI platform ecosystem.