SB2021091317 - HTTP request smuggling in Apache HTTP Server

Description

This security bulletin contains information about 1 vulnerability.

1) Inconsistent interpretation of HTTP requests (CVE-ID: CVE-2021-33193)

CWE-ID: CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling')

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to preform HTTP/2 request smuggling attacks.

The vulnerability exists due to improper validation of HTTP/2 requests in mod_proxy in Apache HTTP Server. A remote attacker can send a specially crafted HTTP/2 request to the server and smuggle arbitrary HTTP headers.

Successful exploitation of vulnerability may allow an attacker to poison web server cache and perform phishing attacks.

Remediation

Install update from vendor's website.

References

• https://portswigger.net/research/http2
• https://github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patch
• https://downloads.apache.org/httpd/CHANGES_2.4