Executive brief
Spring Framework applications using WebSocket connections may leak sensitive request headers in error messages. When a WebSocket connection fails, the framework inadvertently includes HTTP headers (which may contain authentication tokens, session IDs, or other credentials) in exception details visible to end users. This could allow an attacker to harvest sensitive information from error responses.
Technical details
The vulnerability is an information disclosure flaw in Spring WebFlux's WebSocket handling. When WebSocket connections encounter errors, the framework includes raw HTTP request headers in the exception reason string. The vulnerable component is the WebSocket protocol handler, which does not sanitize headers before exposing them in error messages. Attack vector is network-based; an attacker can trigger a WebSocket connection error and observe the exception response to extract headers. No authentication is required. The impact allows retrieval of potentially sensitive headers such as Authorization, Cookie, or custom authentication tokens. Patches are available for all affected versions.
Affected products
- VMware Spring Framework 7.0.0 - 7.0.8, 6.2.0 - 6.2.19, 6.1.0 - 6.1.28, 6.0.0 - 6.0.30, 5.3.0 - 5.3.49, 5.2.25.RELEASE and earlier
Timeline
- 2026-08-27: disclosed