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HIGH

CVE-2019-16785

CVSS v3

7.5

HIGH

EPSS Score

2.5 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • waitressPyPIall versions · fixed in 1.4.0

Vendor advisories

  • CVE-2019-16785 Red Hat Product Security13 products fixed · 7 known affected

    waitress: HTTP request smuggling through LF vs CRLF handling

    python-waitress.src as a component of Red Hat Ceph Storage 3 · python-waitress.src as a component of Red Hat Ceph Storage 4 · python3-waitress as a component of Red Hat Ceph Storage 4

  • RHSA-2021:0420 Red Hat Product Security11 products fixed

    Red Hat Security Advisory: Red Hat Quay v3.4.0 security update

  • RHSA-2020:0720 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: python-waitress security update

Full record on NVD

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.

Technical details

Published
2019-12-20

Frequently asked questions

What is CVE-2019-16785?

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.

Is CVE-2019-16785 actively exploited?

Active exploitation of CVE-2019-16785 has not been confirmed. Its EPSS score was 2.5% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2019-16785?

CVE-2019-16785 has a CVSS v3 base score of 7.5 (HIGH severity).

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