{"cve":"CVE-2019-18277","nvd":{"published":"2019-10-23T14:15:10.557","modified":"2026-06-17T02:24:44.453","status":"Modified","description":"A flaw was found in HAProxy before 2.0.6. In legacy mode, messages featuring a transfer-encoding header missing the \"chunked\" value were not being correctly rejected. The impact was limited but if combined with the \"http-reuse always\" setting, it could be used to help construct an HTTP request smuggling attack against a vulnerable component employing a lenient parser that would ignore the content-length header as soon as it saw a transfer-encoding one (even if not entirely valid according to the specification).","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":7.5},"cwes":["CWE-444"],"references":["http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00016.html","http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00019.html","https://git.haproxy.org/?p=haproxy-2.0.git%3Ba=commit%3Bh=196a7df44d8129d1adc795da020b722614d6a581","https://lists.debian.org/debian-lts-announce/2022/05/msg00045.html","https://nathandavison.com/blog/haproxy-http-request-smuggling"],"products":["haproxy:haproxy"],"source":"nvd","synced_at":"2026-10-19T20:59:10.855360465+00:00"},"epss":{"cve":"CVE-2019-18277","score":0.10068,"percentile":0.95628,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}