Executive brief
Spring Authorization Server, a framework component used to implement OAuth 2.0 and OpenID Connect authentication in Java applications, contains an insufficient validation flaw in its authorization endpoint. An attacker can craft a malicious request with an invalid request_uri parameter paired with an unvalidated redirect_uri to redirect authenticated users to attacker-controlled sites, potentially enabling phishing, credential theft, or malware distribution.
Technical details
The vulnerability is an open redirect flaw in Spring Authorization Server versions 1.5.0 through 1.5.7 in the authorization endpoint's handling of the request_uri parameter. The authorization endpoint performs insufficient validation when processing authorization requests with invalid request_uri values paired with unvalidated redirect_uri parameters, allowing an attacker to specify a redirect destination outside the intended application. This is a server-side open redirect vulnerability that can be exploited via a crafted HTTP request to the authorization endpoint; no authentication or user interaction (beyond the OAuth flow itself) is required. An attacker can use this to redirect users to arbitrary external sites during the OAuth authentication flow. Patches are available in versions 1.5.8 and later.
Affected products
- Spring Authorization Server 1.5.0 through 1.5.7
Timeline
- 2026-08-27: disclosed
- 2026-06-09: patched: version 1.5.8 released