{"id":"CVE-2026-46431","aliases":["GHSA-hw27-4v2q-5qff","GO-2026-5440"],"url":"https://o3.security/vulnerability/CVE-2026-46431","summary":"Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: *","details":"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.","published":"2026-05-26T16:42:40.675Z","modified":"2026-08-12T03:51:21.296893590Z","cvss":{"score":4.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N"},"epss":{"score":0.00219,"percentile":0.12703,"asOf":"2026-08-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/xyproto/algernon","fixedVersion":"1.17.7"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46431.json"},{"type":"ADVISORY","url":"https://github.com/xyproto/algernon/security/advisories/GHSA-hw27-4v2q-5qff"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-46431"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:21.296893590Z"}}