CVE-2026-46431

Published May 26th, 2026

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CVSS v3

4.3

MEDIUM

CVSS v2

N/A

Affected

PROJECT

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.

xyproto/algernon

Small self-contained pure-Go web server with Lua, Teal, Markdown, Ollama, HTTP/2, QUIC, Redis, TypeScript, SQLite and PostgreSQL support ++

GitHub

3.01K