{"cve":"CVE-2019-16785","nvd":{"published":"2019-12-20T23:15:11.167","modified":"2026-06-17T02:22:48.017","status":"Modified","description":"Waitress through version 1.3.1 implemented a \"MAY\" part of the RFC7230 which states: \"Although the line terminator for the start-line and header fields is the sequence CRLF, a recipient MAY recognize a single LF as a line terminator and ignore any preceding CR.\" Unfortunately if a front-end server does not parse header fields with an LF the same way as it does those with a CRLF it can lead to the front-end and the back-end server parsing the same HTTP message in two different ways. This can lead to a potential for HTTP request smuggling/splitting whereby Waitress may see two requests while the front-end server only sees a single HTTP message. This issue is fixed in Waitress 1.4.0.","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":["https://access.redhat.com/errata/RHSA-2020:0720","https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes","https://github.com/Pylons/waitress/commit/8eba394ad75deaf9e5cd15b78a3d16b12e6b0eba","https://github.com/Pylons/waitress/security/advisories/GHSA-pg36-wpm5-g57p","https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html"],"products":["agendaless:waitress","debian:debian_linux","fedoraproject:fedora","oracle:communications_cloud_native_core_network_function_cloud_native_environment","redhat:openstack"],"source":"nvd","synced_at":"2026-10-19T20:59:27.069234358+00:00"},"epss":{"cve":"CVE-2019-16785","score":0.02537,"percentile":0.84948,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-pg36-wpm5-g57p","url":"https://osv.dev/vulnerability/GHSA-pg36-wpm5-g57p","summary":"HTTP Request Smuggling: LF vs CRLF handling in Waitress","modified":"2026-09-10T03:49:24.779958466Z","packages":[{"ecosystem":"PyPI","name":"waitress","purl":"pkg:pypi/waitress","ranges":["<1.4.0"],"fixed":["1.4.0"]}]},{"id":"PYSEC-2019-136","url":"https://osv.dev/vulnerability/PYSEC-2019-136","summary":"","modified":"2023-11-08T04:01:21.641524Z","packages":[{"ecosystem":"PyPI","name":"waitress","purl":"pkg:pypi/waitress","ranges":["<1.4.0"],"fixed":["1.4.0"]}]}],"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."]}