Security advisory
Waitress through version 1.3.1 would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header instead. According to the HTTP standard Transfer-Encoding should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with chunked. Requests sent with: "Transfer-Encoding: gzip, chunked" would incorrectly get ignored, and the request would use a Content-Length header instead to determine the body size of the HTTP message. This could allow for Waitress to treat a single request as multiple requests in the case of HTTP pipelining. This issue is fixed in Waitress 1.4.0.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2019-16786
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 10:46 UTC · Revision 1
Source evidence
Waitress through version 1.3.1 would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header instead. According to the HTTP standard Transfer-Encoding should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with chunked. Requests sent with: "Transfer-Encoding: gzip, chunked" would incorrectly get ignored, and the request would use a Content-Length header instead to determine the body size of the HTTP message. This could allow for Waitress to treat a single request as multiple requests in the case of HTTP pipelining. This issue is fixed in Waitress 1.4.0.
osv:CVE-2019-16786
Complete source record
{
"id": "b226774375fa656023f8788b998003062154bde8ab5328a8a1c7aa68f990c603",
"url": "https://osv.dev/vulnerability/CVE-2019-16786",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2019-16786",
"summary": "Waitress through version 1.3.1 would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header instead. According to the HTTP standard Transfer-Encoding should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with chunked. Requests sent with: \"Transfer-Encoding: gzip, chunked\" would incorrectly get ignored, and the request would use a Content-Length header instead to determine the body size of the HTTP message. This could allow for Waitress to treat a single request as multiple requests in the case of HTTP pipelining. This issue is fixed in Waitress 1.4.0.",
"evidence": "osv:CVE-2019-16786",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2019-16786",
"aliases": [
"CVE-2019-16786",
"GHSA-g2xc-35jw-c63p",
"PYSEC-2019-137"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/pylons/waitress",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "05e965e02f9d73fa6db18a120da1bebcfe429ca2"
},
{
"fixed": "f11093a6b3240fc26830b6111e826128af7771c3"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:agendaless:waitress:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"fixed": "1.3.1"
}
],
"source": "CPE_RANGE"
},
{
"range": [
{
"fixed": "f11093a6b3240fc26830b6111e826128af7771c3"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"versions": [
"v1.3.0",
"v1.3.0b0",
"v1.2.1",
"v1.2.0",
"v1.2.0b3",
"v1.2.0b2",
"v1.2.0b1",
"v1.1.0",
"v1.0.2",
"v1.0.1",
"v1.0.0",
"v1.0a2",
"v1.0a1",
"v0.9.0",
"v0.9.0b1",
"0.9.0b0",
"0.8.11b0",
"0.8.10",
"0.8.9",
"0.8.8",
"0.8.7",
"0.8.6",
"0.8.5",
"0.8.4",
"0.8.3",
"0.8.2",
"0.8.1",
"0.8",
"0.7",
"0.6.1",
"0.6",
"0.5",
"0.4",
"0.3",
"0.2",
"0.1"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2019-16786.json"
}
}
],
"modified": "2026-10-20T10:51:37.815669335Z",
"provider": "osv",
"references": [
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GVDHR2DNKCNQ7YQXISJ45NT4IQDX3LJ7/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LYEOTGWJZVKPRXX2HBNVIYWCX73QYPM5/",
"https://access.redhat.com/errata/RHSA-2020:0720",
"https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes",
"https://github.com/Pylons/waitress/security/advisories/GHSA-g2xc-35jw-c63p",
"https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html",
"https://github.com/Pylons/waitress/commit/f11093a6b3240fc26830b6111e826128af7771c3",
"https://www.oracle.com/security-alerts/cpuapr2022.html"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
"cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*"
],
"vendor_product": "debian:debian_linux",
"extracted_events": [
{
"range": [
{
"introduced": "9.0"
},
{
"last_affected": "9.0"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*",
"cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*"
],
"vendor_product": "fedoraproject:fedora",
"extracted_events": [
{
"range": [
{
"introduced": "30"
},
{
"last_affected": "30"
},
{
"introduced": "31"
},
{
"last_affected": "31"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:oracle:communications_cloud_native_core_network_function_cloud_native_environment:1.10.0:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:communications_cloud_native_core_network_function_cloud_native_environment",
"extracted_events": [
{
"range": [
{
"introduced": "1.10.0"
},
{
"last_affected": "1.10.0"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:redhat:openstack:15:*:*:*:*:*:*:*"
],
"vendor_product": "redhat:openstack",
"extracted_events": [
{
"range": [
{
"introduced": "15"
},
{
"last_affected": "15"
}
],
"source": "CPE_STRING"
}
]
}
]
}
},
"related_cves": [
{
"value": "CVE-2019-16786",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 382684,
"published_at": "2019-12-20T23:15:11.277+00:00"
}