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.
CVSS 4.3EPSS 0.219%Risk 0.44
View source- Published
- 2026-05-26 17:16:51
- Affected versions
- <1.17.7
- Type
- Core software
- Last modified
- 2026-07-24 11:10:00
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N