Inconsistent interpretation of HTTP requests in waitress - CVE-2019-16785
Published: December 21, 2019 / Updated: August 3, 2020
Vulnerability details
The vulnerability allows a remote non-authenticated attacker to manipulate data.
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.
Affected software
py3-waitress (Alpine package)
python-waitress
Fedora
How to mitigate CVE-2019-16785
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/8eba394ad75deaf9e5cd15b78a3d16b12e6b0eba
- https://github.com/Pylons/waitress/security/advisories/GHSA-pg36-wpm5-g57p
- 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/