{"id":"CVE-2026-59249","summary":"Sign-tolerant HTTP/1 chunk-size parser in Mint enables response smuggling against strict intermediaries on pooled connections","details":"Inconsistent interpretation of HTTP requests (HTTP response smuggling) vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a strict intermediary and the Mint client on the same pooled connection, enabling response-queue poisoning against subsequent requests that share the connection.\n\nThe Mint.HTTP1.decode_body/5 function in lib/mint/http1.ex parses the chunk-size line of a Transfer-Encoding: chunked response with Integer.parse(data, 16). RFC 7230 defines chunk-size = 1*HEXDIG and forbids any sign prefix, but Integer.parse/2 accepts an optional leading + or -. A chunk-size line of +5 is accepted as a five-byte chunk; lines of +0 and -0 are accepted as the terminating zero-length chunk and end the message body early.\n\nAn RFC-strict intermediary in the response path rejects these forms, so the intermediary and the Mint client disagree on where one response ends and the next begins. On a pooled keep-alive connection, an attacker-influenced origin can inject bytes that the client attributes to the next legitimate response on the same connection, poisoning the response queue and corrupting the responses returned to unrelated in-flight requests.\n\nThis issue affects mint: from 0.1.0 before 1.9.3.","aliases":["EEF-CVE-2026-59249","GHSA-x3x7-96vm-6h2w"],"modified":"2026-08-07T11:46:41.677465121Z","published":"2026-07-16T11:39:29.939Z","database_specific":{"cna_assigner":"EEF","cwe_ids":["CWE-444"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59249.json","unresolved_ranges":[{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"60089586ec7adc9fddb09f69a2f5919ba9ac7f33"},{"fixed":"fc7d16538db7e40b56ed489f08683225cb0197fa"}]}]},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-59249.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-59249"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59249.json"},{"type":"ADVISORY","url":"https://github.com/elixir-mint/mint/security/advisories/GHSA-x3x7-96vm-6h2w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59249"},{"type":"FIX","url":"https://github.com/elixir-mint/mint/commit/fc7d16538db7e40b56ed489f08683225cb0197fa"},{"type":"PACKAGE","url":"https://github.com/elixir-mint/mint"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/elixir-mint/mint","events":[{"introduced":"47889857fb36f07606ad9c2e52080d202d419058"},{"fixed":"f0b72c0b2363c98d0a220019d108ac6141715428"},{"fixed":"fc7d16538db7e40b56ed489f08683225cb0197fa"}],"database_specific":{"extracted_events":[{"introduced":"0.1.0"},{"fixed":"1.9.3"}],"source":["DESCRIPTION","REFERENCES"]}}],"versions":["v1.9.2","v1.9.1","v1.9.0","v1.8.0","v1.7.1","v1.7.0","v1.6.2","v1.6.1","v1.6.0","v1.5.2","v1.5.1","v1.5.0","v1.4.2","v1.4.1","v1.4.0","v1.3.0","v1.2.1","v1.2.0","v1.1.0","v1.0.0","v0.5.0","v0.4.0","v0.2.1","v0.2.0","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-59249.json"}}],"schema_version":"1.8.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N"}]}