The web server must disable HTTP/1.x downgrading.
An XCCDF Rule
Description
HTTP/2 is backward compatible with HTTP/1.x, so it is possible to configure the architecture to implement a front-end server for HTTP/2 while communicating with one or more back-end servers that support only HTTP/1.x. Thus, the front end effectively has to translate or downgrade the requests it receives into the less secure protocol. HTTP downgrading negates the benefits of HTTP/2. If HTTP downgrading cannot be avoided, validate the rewritten/downgraded request against the HTTP/1.1 specification. For example, reject requests that contain newlines in the headers, colons in header names, and spaces in the request method.
- ID
- SV-264363r984434_rule
- Version
- SRG-APP-000439-WSR-000193
- Severity
- Medium
- References
- Updated
Remediation Templates
A Manual Procedure
Configure the web server to disable HTTP/1.x downgrading.
If HTTP downgrading is operationally necessary, validate the rewritten request against the HTTP/1.1 specification, i.e., reject requests that contain new lines in the headers, colons in header names, and spaces in the request method.