Inconsistent interpretation of HTTP requests in Apache HTTP Server - CVE-2021-33193
Published: September 13, 2021 / Updated: October 2, 2024
Vulnerability identifier: #VU56474
CSH Severity: Medium
CVSS v4.0: 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
CVE-ID: CVE-2021-33193
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Apache Foundation
Affected software:
Apache HTTP Server
Apache HTTP Server
Detailed vulnerability description
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.
How to mitigate CVE-2021-33193
Install update from vendor's website.