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.
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Affected Vendors & Products
References
History
Tue, 26 May 2026 19:30:00 +0000
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Tue, 26 May 2026 17:00:00 +0000
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| 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. | |
| Title | Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: * | |
| Weaknesses | CWE-942 | |
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cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-05-26T17:39:14.529Z
Reserved: 2026-05-13T22:18:22.830Z
Link: CVE-2026-46431
Updated: 2026-05-26T17:39:03.913Z
Status : Deferred
Published: 2026-05-26T17:16:51.100
Modified: 2026-05-26T19:26:42.643
Link: CVE-2026-46431
No data.
OpenCVE Enrichment
Updated: 2026-05-26T18:45:13Z