{"cve":"CVE-2019-16789","nvd":{"published":"2019-12-26T17:15:13.707","modified":"2026-06-17T02:22:48.410","status":"Modified","description":"In Waitress through version 1.4.0, if a proxy server is used in front of waitress, an invalid request may be sent by an attacker that bypasses the front-end and is parsed differently by waitress leading to a potential for HTTP request smuggling. Specially crafted requests containing special whitespace characters in the Transfer-Encoding header would get parsed by Waitress as being a chunked request, but a front-end server would use the Content-Length instead as the Transfer-Encoding header is considered invalid due to containing invalid characters. If a front-end server does HTTP pipelining to a backend Waitress server this could lead to HTTP request splitting which may lead to potential cache poisoning or unexpected information disclosure. This issue is fixed in Waitress 1.4.1 through more strict HTTP field validation.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N","score":8.2},"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/11d9e138125ad46e951027184b13242a3c1de017","https://github.com/github/advisory-review/pull/14604","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-2019-16789","score":0.02587,"percentile":0.85258,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-968f-66r5-5v74","url":"https://osv.dev/vulnerability/GHSA-968f-66r5-5v74","summary":"HTTP Request Smuggling in Waitress: Invalid whitespace characters in headers (Follow-up)","modified":"2024-11-19T14:00:55.884655Z","packages":[{"ecosystem":"PyPI","name":"waitress","purl":"pkg:pypi/waitress","ranges":["<1.4.2"],"fixed":["1.4.2"]}]},{"id":"PYSEC-2019-138","url":"https://osv.dev/vulnerability/PYSEC-2019-138","summary":"","modified":"2023-11-08T04:01:21.767656Z","packages":[{"ecosystem":"PyPI","name":"waitress","purl":"pkg:pypi/waitress","ranges":["<1.4.1"],"fixed":["1.4.1"]}]}],"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."]}