CVE-2019-16786 — Waitress through version 1

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 separ

01What is this vulnerability?

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…

02Affected products

Vendor	Product	Versions
Pylons	Waitress	<= 1.3.1

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2019-12-20T23:00:20.000Z
• Last modified: 2024-08-05T01:24:48.017Z

09References

• lists.fedoraproject.org — https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro…
• lists.fedoraproject.org — https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro…
• access.redhat.com — https://access.redhat.com/errata/RHSA-2020:0720
• www.oracle.com — https://www.oracle.com/security-alerts/cpuapr2022.html
• docs.pylonsproject.org — https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes
• github.com — https://github.com/Pylons/waitress/security/advisories/GHSA-g2xc-35jw-c63p
• github.com — https://github.com/Pylons/waitress/commit/f11093a6b3240fc26830b6111e826128af7771…
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html