{"id":"CVE-2026-46431","state":"PUBLISHED","title":"Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: *","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.","publishedAt":"2026-05-26T16:42:40.675Z","updatedAt":"2026-05-26T17:39:14.529Z","severity":{"score":4.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["xyproto algernon"],"affected":[{"vendor":"xyproto","product":"algernon","versions":[{"version":"< 1.17.7","status":"affected"}]}],"references":["https://github.com/xyproto/algernon/security/advisories/GHSA-hw27-4v2q-5qff"],"weaknesses":["CWE-942"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/46xxx/CVE-2026-46431.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-46431","state":"PUBLISHED","datePublished":"2026-05-26T16:42:40.675Z","dateUpdated":"2026-05-26T17:39:14.529Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-05-13T22:18:22.830Z"},"containers":{"cna":{"title":"Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: *","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"xyproto","product":"algernon","versions":[{"version":"< 1.17.7","status":"affected"}]}],"references":[{"url":"https://github.com/xyproto/algernon/security/advisories/GHSA-hw27-4v2q-5qff","name":"https://github.com/xyproto/algernon/security/advisories/GHSA-hw27-4v2q-5qff","tags":["x_refsource_CONFIRM"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":4.3,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-942","lang":"en","description":"CWE-942: Permissive Cross-domain Policy with Untrusted Domains","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-05-26T16:42:40.675Z"},"source":{"advisory":"GHSA-hw27-4v2q-5qff","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/xyproto/algernon/security/advisories/GHSA-hw27-4v2q-5qff","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-26T17:38:47.158630Z","id":"CVE-2026-46431","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-05-26T17:39:14.529Z"}}]}}}