bugtraq - Nginx ngx_http_close_connection function integer overflow

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Date: Thu, 25 Apr 2013 06:52:19 GMT
From: safe3q@...il.com
To: bugtraq@...urityfocus.com
Subject: Nginx ngx_http_close_connection function integer overflow

Website: http://safe3.com.cn

I. BACKGROUND
---------------------

Nginx is an HTTP and reverse proxy server, as well as a mail proxy server, written by Igor Sysoev. For a long time, it has been running on many heavily loaded Russian sites including Yandex, Mail.Ru, VKontakte, and Rambler. According to Netcraft nginx served or proxied 12.96% busiest sites in April 2013. Here are some of the success stories: Netflix, Wordpress.com, FastMail.FM.

II. DESCRIPTION
---------------------

Qihoo 360 Web Security Research Team discovered a critical vulnerability in nginx.

The vulnerability is caused by a int overflow error within the Nginx
ngx_http_close_connection function  when r->count is less then 0 or more then 255, which could be exploited
by remote attackers to compromise a vulnerable system via malicious http requests.

III. AFFECTED PRODUCTS
---------------------------

Nginx all latest version

IV. Exploits/PoCs
---------------------------------------

In-depth technical analysis of the vulnerability and a fully functional remote code execution exploit are available through the safe3q@...il.com
In src\http\ngx_http_request_body.c ngx_http_discard_request_body function,we can make r->count++.

V. VUPEN Threat Protection Program
-----------------------------------

VI. SOLUTION
----------------

Validate the r->count input.

VII. CREDIT
--------------

This vulnerability was discovered by Safe3 of Qihoo 360.

VIII. ABOUT Qihoo 360
---------------------------

Qihoo 360 is the leading provider of defensive and offensive web cloud security of China.

IX. REFERENCES
----------------------
http://nginx.org/en/