CVE-2026-46431
Medium
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.
SeverityMedium
CVSS4.3
Exploit probability—
ProductGithub.com/xyproto/algernon
PublishedMay 26, 2026
First seenMay 26, 2026
Weakness typeCWE-942CWE-942
How to fix
Update
- github.com/xyproto/algernon1.17.7 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| github.com/xyproto/algernonGo | v < 1.17.7 | 1.17.7 |
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