title: HTTP Request Smuggling: LF vs CRLF handling in Waitress
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.
problem types: CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling')
affected:
{
product: Waitress
vendor: Pylons
versions:
lessThanOrEqual: 1.3.1, status: affected, version: <= 1.3.1, versionType: custom
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: NONE
baseScore: 7.1
baseSeverity: HIGH
confidentialityImpact: HIGH
integrityImpact: LOW
privilegesRequired: LOW
scope: CHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N
version: 3.1
]