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Fencer Vulns
high 7.1

CVE-2019-16789 json

HTTP Request Smuggling in Waitress: Invalid whitespace characters in headers

published 2019-12-26 6 y ago modified 2026-06-17 4 mo ago also GHSA-968f-66r5-5v74 , PYSEC-2019-138 , EUVD-2019-0158

cvss
7.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.6%
EPSS 2.6% chance of exploitation in 30 days, percentile 85%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi waitress 1.4.1, 1.4.2
  • Pylons Waitress 1.4.1
  • waitress Debian 14, Debian 13, Debian 12 1.4.1-1

debian advisories DEBIAN-CVE-2019-16789

  • python-waitress openstack 15 1.4.2-1.el8ost
  • python3-waitress openstack 15 1.4.2-1.el8ost

red hat advisories RHSA-2020:0720

  • python-waitress SLE Module for Package Hub 15 SP2, SLE Module for Package Hub 15 SP1, SLE Module for Basesystem 15 SP2 +6 more 1.4.3-3.3.1
  • kibana OpenStack Cloud Crowbar 9, OpenStack Cloud 9 4.6.3-4.3.2
  • grafana OpenStack Cloud Crowbar 9, OpenStack Cloud 9 6.2.5-3.12.2
  • ansible1 OpenStack Cloud 9 1.9.6-9.7.2
  • ardana-mq OpenStack Cloud 9 9.0+git.1593618110.cbd1a37-3.16.2
  • crowbar-core OpenStack Cloud Crowbar 9 6.0+git.1594619891.b75a61d0d-3.25.5
  • rubygem-puma OpenStack Cloud Crowbar 9 2.16.0-4.9.1
  • ardana-glance OpenStack Cloud 9 9.0+git.1593631708.9354a78-3.13.2

suse advisories SUSE-SU-2020:3292-1SUSE-SU-2020:3269-1SUSE-RU-2020:2161-1SUSE-RU-2020:2072-1SUSE-SU-2020:1901-1

  • python-waitress openSUSE Leap 15.1 1.4.3-lp151.3.3.1
  • python-waitress openSUSE Leap 15.2 1.4.3-lp152.4.3.1

opensuse advisories openSUSE-SU-2020:1922-1openSUSE-SU-2020:1911-1

  • py3-waitress Alpine 3.24, Alpine 3.23, Alpine 3.22 +11 more 1.4.1-r0

alpine advisories ALPINE-CVE-2019-16789

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2019-16789 updated cvss 8.2

waitress: HTTP Request Smuggling through Invalid whitespace characters in headers

  • Red Hat Ceph Storage 3 python-waitress Red Hat Ceph Storage 4 python-waitress, python3-waitress
    affected: no fix available “Fix deferred”
  • Red Hat OpenStack Platform 13 (Queens) python-waitress, python2-waitress
    affected: no fix planned “Will not fix”
  • Red Hat OpenStack Platform 16 (Train) python-waitress, python3-waitress
    affected: no fix available
  • Red Hat Quay v3 quay/quay-rhel8 v3.4.0-51, quay/clair-rhel8 v3.4.0-25, quay/quay-builder-rhel8 v3.4.0-18, quay/quay-operator-bundle v3.4.0-89, quay/quay-operator-rhel8 v3.4.0-132, quay/quay-bridge-operator-bundle v3.4.0-3, +5 more
    fixed: vendor fix RHSA-2021:0420
  • Red Hat OpenStack Platform 15.0 python-waitress 1.4.2-1.el8ost, python3-waitress 1.4.2-1.el8ost
    fixed: vendor fix RHSA-2020:0720

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.59% chance of exploitation in the next 30 days, higher than 85% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:H/A:N
NVD 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
NVD 2.0 6.4 AV:N/AC:L/Au:N/C:P/I:P/A:N
GitHub 3.1 7.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:H/A:N

Affected packages

ecosystem package affected fixed in
pypi waitress
<1.4.2
<1.4.1
1.4.2
1.4.1

Affected products

  • Pylons Waitress

Classification

Weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.