CVE-2022-32149 represents a newly discovered security vulnerability that can result in a Denial of Service (DoS) attack on certain web servers. The attack vector uses a maliciously crafted Accept-Language header to exploit inefficiencies in the parsing process. In this long read, we'll explore the details of this vulnerability, explain how an attacker could exploit it, and discuss potential mitigation strategies. We'll also examine some relevant code snippets and provide links to original reference materials.
Section 1: Understanding the Accept-Language Header
The Accept-Language header is an HTTP header field that allows clients to specify their desired language preferences for a website's content. When visiting a web page, browsers typically send this header to inform the server which languages the user understands, and in what order of preference. The server then uses this information to deliver content in the most suitable language for the browser.
Here's an example of a regular Accept-Language header
Accept-Language: en-US, en;q=.9
In this case, the browser is signaling that it prefers content in US English and will also accept content in English as a secondary preference.
Section 2: The Vulnerability - CVE-2022-32149
The vulnerability, identified as CVE-2022-32149, occurs when a malicious actor crafts a specially designed Accept-Language header that takes an exceptionally long time for the server to parse. This prolonged parsing time results in high CPU usage on the server, effectively causing a denial of service. Essentially, the server becomes unable to process new incoming requests, leading to degraded performance or a complete halt.
To understand the mechanics of the vulnerability, consider the following example of an attacker's crafted Accept-Language header:
Accept-Language: a;q=.1,*;q=.9,aacc;q=.8,b;q=.2...[many more entries]...
In this case, the attacker carefully positions low-quality preference options within the header, forcing the server to spend considerable resources sorting them, which in turn leads to high CPU usage.
Section 3: Exploit Details
The exploitation of this vulnerability is simple, as it only requires sending this maliciously crafted Accept-Language header along with the HTTP requests to the targeted server..awtextra
Published on: 10/14/2022 15:15:00 UTC
Last modified on: 10/18/2022 17:41:00 UTC