{"id":"EEF-CVE-2026-47066","summary":"Infinite loop in Alt-Svc header parser in hackney","details":"## Summary\n\nLoop 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":["CVE-2026-47066","GHSA-6cp8-v795-jr2j"],"modified":"2026-05-26T19:46:40.305Z","published":"2026-05-25T14:00:39.707Z","database_specific":{"cwe_ids":["CWE-835"],"cpe_ids":["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"],"capec_ids":["CAPEC-130"]},"references":[{"type":"ADVISORY","url":"https://github.com/benoitc/hackney/security/advisories/GHSA-6cp8-v795-jr2j"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-47066.html"},{"type":"FIX","url":"https://github.com/benoitc/hackney/commit/e548aba1f97ffa3f4750da7b772998fb78c01894"},{"type":"PACKAGE","url":"https://hex.pm/packages/hackney"}],"affected":[{"package":{"name":"hackney","ecosystem":"Hex","purl":"pkg:hex/hackney"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.0.0-beta.1"},{"fixed":"4.0.1"}]}],"versions":["2.0.0","2.0.0-beta.1","2.0.1","3.0.0","3.0.1","3.0.2","3.0.3","3.1.0","3.1.1","3.1.2","3.2.0","3.2.1","4.0.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-47066.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/benoitc/hackney","events":[{"introduced":"408e5fe20302226ea8c74dde2bcbd452d712b5b2"},{"fixed":"e548aba1f97ffa3f4750da7b772998fb78c01894"}]}],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-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"}],"credits":[{"name":"Peter Ullrich","type":"FINDER"},{"name":"Benoit Chesneau","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen","type":"ANALYST"}]}