search menu icon-carat-right cmu-wordmark

CERT Coordination Center

HTTP CONNECT and 407 Proxy Authentication Required messages are not integrity protected

Vulnerability Note VU#905344

Original Release Date: 2016-08-15 | Last Revised: 2018-04-04

Overview

HTTP CONNECT requests and 407 Proxy Authentication Required messages are not integrity protected and are susceptible to man-in-the-middle attacks. WebKit-based applications are additionally vulnerable to arbitrary HTML markup and JavaScript execution in the context of the originally requested domain.

Description

Web browsers and operating systems making a HTTPS request via a proxy server are vulnerable to man-in-the-middle (MITM) attacks against HTTP CONNECT requests and proxy response messages. HTTP CONNECT requests are made in clear text over HTTP, meaning an attacker in the position to modify proxy traffic may force the use of 407 Proxy Authentication Required responses to phish for credentials.

WebKit-based clients are vulnerable to additional vectors due to the fact that HTML markup and JavaScript are rendered by the client Document Object Model (DOM) in the context of the originally requested HTTPS domain.

For more information, refer to the FalseCONNECT website.

Impact

An attacker in the position to control HTTP CONNECT requests and proxy responses can conduct MITM attacks, which may include credential phishing and, where vulnerable WebKit-based clients are involved, arbitrary HTML and JavaScript injection.

Solution

Apply an update

Check with affected software vendors and apply an update, if available. Those unable or unwilling to apply an update should consider the following workarounds.

Avoid untrusted networks

Avoid using proxy-configured clients while connected to untrusted networks, including public WiFi. Using a proxy-configured client on an untrusted network increases the chance of falling victim to a MITM attack.

Disable proxy configuration settings

If use of proxy auto-configuration (PAC) or web proxy auto-discovery (WPAD) is not required, consider disabling them.

Vendor Information

905344
 

View all 44 vendors View less vendors


CVSS Metrics

Group Score Vector
Base 4.3 AV:A/AC:M/Au:N/C:P/I:P/A:N
Temporal 3.4 E:POC/RL:OF/RC:C
Environmental 3.4 CDP:ND/TD:H/CR:ND/IR:ND/AR:ND

References

Acknowledgements

Thanks to Jerry Decime for reporting these vulnerabilities.

This document was written by Joel Land.

Other Information

CVE IDs: None
Date Public: 2016-08-15
Date First Published: 2016-08-15
Date Last Updated: 2018-04-04 18:12 UTC
Document Revision: 35

Sponsored by CISA.