{"id":"CVE-2026-47066","summary":"Infinite loop in Alt-Svc header parser in hackney","details":"Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in benoitc hackney allows Excessive Allocation. The Alt-Svc response header parser in src/hackney_altsvc.erl does not guarantee forward progress. When parse_token/2 receives a non-token, non-whitespace, non-comma byte (e.g. !, @, =, ;), it returns the input unchanged. skip_comma/1 also returns the buffer unchanged when the first byte is not a comma. parse_entries/2 then recurses with identical data, creating a tight infinite tail-recursive loop that pins a scheduler at 100% CPU. The calling process never returns.\n\nThe entry point parse_and_cache/3 is called synchronously in the connection process on every HTTP response. A single-byte Alt-Svc: ! response header is sufficient to trigger the hang; the header is fully controlled by any HTTP origin the client connects to.\n\nThis issue affects hackney: from 2.0.0-beta.1 before 4.0.1.","aliases":["EEF-CVE-2026-47066","GHSA-6cp8-v795-jr2j"],"modified":"2026-07-08T08:13:38.633947345Z","published":"2026-05-25T14:00:39.707Z","database_specific":{"cwe_ids":["CWE-835"],"unresolved_ranges":[{"extracted_events":[{"introduced":"408e5fe20302226ea8c74dde2bcbd452d712b5b2"},{"fixed":"e548aba1f97ffa3f4750da7b772998fb78c01894"}],"source":"AFFECTED_FIELD"}],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47066.json","cna_assigner":"EEF"},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-47066.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-47066"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47066.json"},{"type":"ADVISORY","url":"https://github.com/benoitc/hackney/security/advisories/GHSA-6cp8-v795-jr2j"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47066"},{"type":"FIX","url":"https://github.com/benoitc/hackney/commit/e548aba1f97ffa3f4750da7b772998fb78c01894"},{"type":"PACKAGE","url":"https://github.com/benoitc/hackney"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/benoitc/hackney","events":[{"introduced":"a7ce34b42892ab305b2ef7dbe873bcabf4ef93ca"},{"fixed":"c41c8d48ace8141b003f6f1de3ca6734a0c53056"},{"fixed":"e548aba1f97ffa3f4750da7b772998fb78c01894"}],"database_specific":{"cpe":"cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"2.0.0"},{"fixed":"4.0.1"}],"source":["CPE_RANGE","REFERENCES"]}}],"versions":["4.0.0","3.2.1","3.2.0","3.1.2","3.1.1","3.1.0","3.0.3","3.0.2","3.0.1","2.0.1","2.0.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-47066.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}