CVE-2026-82438: Apache Storm Webapp: Authenticated API Responses Exposed to Arbitrary Web Origins
Description
Three separate mechanisms allowed a web page on an unrelated origin to read responses that Storm's HTTP components served to an authenticated user.
The Logviewer reflected the request's Origin header back in Access-Control-Allow-Origin while also sending Access-Control-Allow-Credentials: true. The published security model documents a permissive Access-Control-Allow-Origin: posture as accepted, which is safe precisely because browsers refuse to honour together with credentials; reflecting the concrete origin removes that protection.
The shared CORS filter used by the UI, the Logviewer and DRPC was configured with a response header name where an initialisation parameter name was expected. The container ignored the setting and applied its own defaults, which allow credentials.
Finally, the UI and Logviewer wrapped API responses in a caller-supplied JSONP callback for every GET request. A script element on any origin can load such a response, which bypasses the same-origin policy entirely rather than negotiating it, and there was no way to turn the behaviour off.
In each case the effect is that a page visited by an authenticated operator can read cluster, topology and log data on their behalf.
Mitigation
Upgrade to 3.1.0, where the Logviewer no longer reflects the request origin in a credentialed response, the CORS filter is configured explicitly, and JSONP wrapping is governed by ui.enable.jsonp, which defaults to false.
Note that disabling JSONP is a behaviour change for tooling that passes a callback query parameter; such tooling should be moved to ordinary JSON requests.
Users who cannot upgrade immediately should place the UI, Logviewer and DRPC HTTP endpoints behind a reverse proxy that strips Access-Control-Allow-Origin and Access-Control-Allow-Credentials from responses and rejects requests carrying a callback parameter.
Credit
The ASF -- found using Claude agents to study the security of open-source projects, validated and reported by Apache Storm.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Apache Storm Webappto a version that resolves this vulnerability.Fixed in 3.1.0 - Configuration
Disable JSONP (set ui.enable.jsonp to false) so authenticated API responses are not wrapped via a caller-supplied JSONP callback parameter; note this changes behavior for tooling that uses the callback query parameter.
Apache Storm Webapp UI ui.enable.jsonp = false - Compensating control
For deployments that cannot upgrade immediately, place the UI, Logviewer, and DRPC HTTP endpoints behind a reverse proxy that strips the response headers Access-Control-Allow-Origin and Access-Control-Allow-Credentials, and rejects requests carrying a callback parameter.
Event History
Frequently Asked Questions
Who is exposed to this issue?
Authenticated Storm operators are exposed if they visit a web page hosted on an unrelated origin. That page can read responses from affected Storm HTTP components using the operator's authenticated browser session.
Which Storm components are involved?
The shared CORS filter affects the UI, Logviewer, and DRPC. The JSONP behavior affects the UI and Logviewer for every GET request.
Does an attacker need direct access to the Storm deployment?
No direct access is described. The attacker needs to cause an authenticated operator to load a page on an unrelated web origin, after which that page can request and read affected responses through the operator's browser.
Can JSONP be disabled as a temporary mitigation?
No. The described UI and Logviewer JSONP behavior had no way to be turned off.
Why does the documented wildcard CORS posture not prevent exposure?
Browsers do not honor Access-Control-Allow-Origin: * together with credentials. Logviewer instead reflected the requesting Origin value while allowing credentials, which permits a concrete unrelated origin to read authenticated responses.