Description
Algernon is a small self-contained pure-Go web server. Prior to 1.17.7, the SSE event server's Access-Control-Allow-Origin response header was hardcoded to the wildcard * regardless of the caller's Origin. Because EventSource does not preflight and does not send cookies, the wildcard is sufficient to let any third-party page the developer visits open a cross-origin EventSource to the SSE port and read the live filename stream from JavaScript. This vulnerability is fixed in 1.17.7.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:NWeakness enumeration
Affected software
No affected versions have been published.
Timeline
- Published
- May 26, 2026
- Last modified
- Jul 24, 2026
- NVD status
- Deferred