Inconsistent interpretation of HTTP requests in waitress - CVE-2019-16786
Published: December 21, 2019 / Updated: July 17, 2020
Vulnerability details
The vulnerability allows a remote non-authenticated attacker to manipulate data.
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.
Affected software
py3-waitress (Alpine package)
python-waitress
Fedora
How to mitigate CVE-2019-16786
py3-waitress (Alpine package) - update to 1.4.1-r0
python-waitress - addressed in versions 1.4.3-1.el7, 1.4.3-1.el8, 1.4.3-1.fc30, 1.4.3-1.fc31
External References
- https://access.redhat.com/errata/RHSA-2020:0720
- https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes
- https://github.com/Pylons/waitress/commit/f11093a6b3240fc26830b6111e826128af7771c3
- https://github.com/Pylons/waitress/security/advisories/GHSA-g2xc-35jw-c63p
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GVDHR2DNKCNQ7YQXISJ45NT4IQDX3LJ7/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LYEOTGWJZVKPRXX2HBNVIYWCX73QYPM5/