{"id":"CVE-2026-65957","summary":"Helio: Dashboard sideband CORS origin allowlist matches hostnames by prefix, admitting attacker-controlled origins in open mode","details":"Helio is an MCP proxy that sits between AI agents and the tools they use. Prior to version 0.8.0, the dashboard sideband (default 127.0.0.1:3100) validated CORS request origins by matching the hostname against a private-network string prefix (10., 172.16.–172.31., 192.168.) rather than validating an IP address. A public DNS name such as 192.168.attacker.com, 10.evil.io, or 172.16.pwn.example also satisfies that prefix, so the proxy echoed the attacker origin in Access-Control-Allow-Origin. This issue has been patched in version 0.8.0.","aliases":["GHSA-2c3r-q7gv-hp2m"],"modified":"2026-11-13T02:47:36.202775852Z","published":"2026-11-11T20:36:21.626Z","database_specific":{"unresolved_ranges":[{"extracted_events":[{"strategy":"StringRangeExpression","range":[{"fixed":"0.8.0"}],"source":"AFFECTED_FIELD"}]},{"extracted_events":[{"range":[{"fixed":"0.8.0"},{"fixed":"0.8.0"}],"source":"DESCRIPTION"}]}],"cna_assigner":"GitHub_M","cwe_ids":["CWE-346","CWE-942"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/65xxx/CVE-2026-65957.json"},"references":[{"type":"WEB","url":"https://github.com/gethelio/helio/releases/tag/v0.8.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/65xxx/CVE-2026-65957.json"},{"type":"ADVISORY","url":"https://github.com/gethelio/helio/security/advisories/GHSA-2c3r-q7gv-hp2m"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-65957"},{"type":"FIX","url":"https://github.com/gethelio/helio/commit/4ca8329c38b0edbc5e4d782a4e3b0cfc5cd7782e"},{"type":"FIX","url":"https://github.com/gethelio/helio/pull/121"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/gethelio/helio","events":[{"introduced":"0"},{"fixed":"4ca8329c38b0edbc5e4d782a4e3b0cfc5cd7782e"},{"fixed":"6f9d147a018caae632be7758b42d1b6073495829"}],"database_specific":{"extracted_events":[{"source":"REFERENCES_COMMIT","range":[{"fixed":"4ca8329c38b0edbc5e4d782a4e3b0cfc5cd7782e"}]},{"source":"REFERENCES_TAG","original_tag":"v0.8.0","range":[{"fixed":"6f9d147a018caae632be7758b42d1b6073495829"}]}]}}],"versions":["v0.7.0","v0.6.0","v0.5.0","v0.4.0","v0.3.0","v0.2.0","v0.1.1","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-65957.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N"}]}