Executive brief
Eclipse Vert.x is a toolkit for building reactive applications on the Java Virtual Machine. A security flaw in its HTTP client component allows sensitive information, such as login credentials, session cookies, and API keys, to be accidentally sent to untrusted third-party servers during a web redirect. An attacker could exploit this to steal user credentials or access tokens by tricking the application into requesting a malicious URL.
Technical details
A vulnerability exists in the DefaultRedirectHandler of vertx-core where request headers are propagated as-is during cross-origin HTTP 30x redirects. The handler fails to perform origin comparison (scheme, host, port) before copying headers, only stripping the Content-Length header. Consequently, sensitive headers such as Authorization, Cookie, Proxy-Authorization, and custom tokens (e.g., X-API-Token) are forwarded to the redirect target. An attacker can exploit this by providing a URL to a component that uses HttpClient (like a webhook or proxy) that redirects to an attacker-controlled server to capture these credentials. The issue affects versions up to 4.5.29 and 5.1.4.
Affected products
- Eclipse Foundation Eclipse Vert.x <= 4.5.29, <= 5.1.4
Timeline
- 2026-07-14: advisory: CVE-2026-15075 published by NVD and Eclipse Foundation