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CVE-2019-16786· NVD / CVE Program· CNA GitHub_M

HTTP Request Smuggling: Invalid Transfer-Encoding in Waitress

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.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Dec 20, 2019
Updated
Jun 16, 2026
EPSS
2.4% · 83th percentile
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Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 2.4%

CNA vs NVD score

NVD
7.5
CNA · GitHub_M
7.1
0.4 point gap

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Noroxi analysis

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Affected systems

VendorProduct
agendalesswaitress
oraclecommunications cloud native core network function cloud native environment
debiandebian linux
fedoraprojectfedora
redhatopenstack

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • agendaless waitressbefore 1.3.1
  • debian debian linux9.0
  • fedoraproject fedora30
  • fedoraproject fedora31
  • oracle communications cloud native core network function cloud native environment1.10.0
  • redhat openstack15

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • Pylons Waitress

    • <= 1.3.1 and later · up to and including 1.3.1affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12waitressbefore 1.4.1-11.4.1-1
Debian:9waitressbefore 1.0.1-1+deb9u11.0.1-1+deb9u1
openSUSE:Leap 15.1python-waitressbefore 1.4.3-lp151.3.3.11.4.3-lp151.3.3.1
openSUSE:Leap 15.2python-waitressbefore 1.4.3-lp152.4.3.11.4.3-lp152.4.3.1
PyPIwaitressbefore 1.4.01.4.0
PyPIwaitressbefore 1.3.11.3.1
Red Hat:openstack:15::el8python-waitressbefore 0:1.4.2-1.el8ost0:1.4.2-1.el8ost
Red Hat:openstack:15::el8python3-waitressbefore 0:1.4.2-1.el8ost0:1.4.2-1.el8ost
SUSE:HPE Helion OpenStack 8ansiblebefore 2.4.6.0-3.9.12.4.6.0-3.9.1
SUSE:HPE Helion OpenStack 8ansible1before 1.9.6-7.3.11.9.6-7.3.1
SUSE:HPE Helion OpenStack 8ardana-ansiblebefore 8.0+git.1589740980.6c3bcdc-3.73.18.0+git.1589740980.6c3bcdc-3.73.1
SUSE:HPE Helion OpenStack 8ardana-clusterbefore 8.0+git.1585685203.3e71e49-3.36.18.0+git.1585685203.3e71e49-3.36.1
SUSE:HPE Helion OpenStack 8ardana-freezerbefore 8.0+git.1586539529.b7d295f-3.21.18.0+git.1586539529.b7d295f-3.21.1
SUSE:HPE Helion OpenStack 8ardana-input-modelbefore 8.0+git.1589740934.0e0ad61-3.39.18.0+git.1589740934.0e0ad61-3.39.1
SUSE:HPE Helion OpenStack 8ardana-loggingbefore 8.0+git.1591194866.b7375d0-3.24.18.0+git.1591194866.b7375d0-3.24.1
SUSE:HPE Helion OpenStack 8ardana-mqbefore 8.0+git.1589715269.62ad6df-3.22.18.0+git.1589715269.62ad6df-3.22.1
SUSE:HPE Helion OpenStack 8ardana-neutronbefore 8.0+git.1590756744.ba84abc-3.42.18.0+git.1590756744.ba84abc-3.42.1
SUSE:HPE Helion OpenStack 8ardana-octaviabefore 8.0+git.1590100427.cf4cc8f-3.29.18.0+git.1590100427.cf4cc8f-3.29.1
SUSE:HPE Helion OpenStack 8ardana-osconfigbefore 8.0+git.1587034587.eac37b8-3.45.18.0+git.1587034587.eac37b8-3.45.1
SUSE:HPE Helion OpenStack 8caasp-openstack-heat-templatesbefore 1.0+git.1560518045.ad7dc6d-4.18.11.0+git.1560518045.ad7dc6d-4.18.1
SUSE:HPE Helion OpenStack 8documentation-hpe-helion-openstack-installationbefore 8.20200527-1.26.18.20200527-1.26.1
SUSE:HPE Helion OpenStack 8documentation-hpe-helion-openstack-operationsbefore 8.20200527-1.26.18.20200527-1.26.1
SUSE:HPE Helion OpenStack 8documentation-hpe-helion-openstack-opsconsolebefore 8.20200527-1.26.18.20200527-1.26.1
SUSE:HPE Helion OpenStack 8documentation-hpe-helion-openstack-planningbefore 8.20200527-1.26.18.20200527-1.26.1

+96

Same product

agendaless: all records

Other highest-scoring records for the same primary product.

  • CVE-2019-16789HTTP Request Smuggling in Waitress: Invalid whitespace characters in headers
    33Monitor
  • CVE-2022-24761HTTP Request Smuggling in waitress
    31Monitor
  • CVE-2019-16792HTTP Request Smuggling: Content-Length Sent Twice in Waitress
    31Monitor
  • CVE-2019-16785HTTP Request Smuggling: LF vs CRLF handling in Waitress
    31Monitor
  • CVE-2024-49769Waitress has a denial of service leading to high CPU usage/resource exhaustion
    30Monitor
  • CVE-2020-5236Catastrophic backtracking in regex allows Denial of Service in Waitress
    27Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:waitress1.4.1-1 · Debian:12Package registry (OSV)
opensuse:python-waitress1.4.3-lp152.4.3.1 · openSUSE:Leap 15.2Package registry (OSV)
PyPI:waitress1.3.1Package registry (OSV)
PyPI:waitress1.4.0Package registry (OSV)
red hat:python-waitress0:1.4.2-1.el8ost · Red Hat:openstack:15::el8Package registry (OSV)
red hat:python3-waitress0:1.4.2-1.el8ost · Red Hat:openstack:15::el8Package registry (OSV)
suse:ansible2.2.3.0-12.2 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:crowbar-core4.0+git.1580209654.1d112d31f-9.66.5 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:crowbar-ha4.0+git.1585316203.d6ad2c8-4.52.4 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:crowbar-openstack4.0+git.1589804581.9972163f0-9.71.4 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:grafana4.6.5-1.14.1 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:keepalived2.0.19-1.8.1 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:kibana4.6.3-5.1 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:memcached1.5.17-3.6.1 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:monasca-installer20180608_12.47-12.1 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:openstack-dashboard-theme-SUSE2016.2-5.12.4 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:openstack-manila3.0.1~dev30-4.12.2 · SUSE:OpenStack Cloud 7Package registry (OSV)
suse:openstack-manila-doc3.0.1~dev30-4.12.3 · SUSE:OpenStack Cloud 7Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records