In today's world, the internet is an essential aspect of our lives, and web applications play a significant role in providing various services through the internet. PHP, as one of the most popular scripting languages, empowers a vast number of web applications. However, web applications and the underlying infrastructure can be vulnerable to numerous security threats. One such vulnerability has been discovered in PHP, and to mitigate risks for the users, it must be well understood and addressed.

This post will discuss the vulnerability identified as CVE-2025-1217, which affects PHP's HTTP request module, particularly in versions 8.1.* before 8.1.32, 8.2.* before 8.2.28, 8.3.* before 8.3.19, and 8.4.* before 8.4.5. We will talk about the issue, the exploits associated with it, and point you to the original sources of information.

PHP HTTP Request Module Vulnerability: Parsing Folded Headers Incorrectly (CVE-2025-1217)

The issue pertains to the incorrect parsing of folded headers when the PHP HTTP response module handles HTTP responses obtained from a server. This might result in the misinterpretation of the response, leading to the use of incorrect headers, MIME types, etc.

To better understand the context, let's look at what folded headers are. In HTTP, headers can sometimes be too long, and to maintain line length limits, they can be broken into multiple lines by using a technique called "header folding". The method involves inserting whitespace or a line break before continuing the header's content on the next line.

Unfortunately, the PHP HTTP request module in the mentioned versions has a bug, which leads to incorrectly parsing folded headers. The code snippet below highlights the faulty portion of the code:

$headers = "Content-Type: text/html; charset=UTF-8\r\n
            Content-Length: 1234\r\n
            Connection: close\r\n";

$headers = explode("\r\n", $headers);

foreach ($headers as $header) {
    $header = trim($header);
    list($key, $value) = explode(': ', $header, 2);
    // Incorrect parsing of folded headers occurs here
}

Exploit Details

This vulnerability may give attackers the opportunity to manipulate the response headers, thereby causing unexpected behavior in web applications developed using the vulnerable PHP versions. Exploits may include:

1. Bypassing security restrictions: An attacker can potentially bypass security mechanisms, such as Content Security Policy (CSP), by injecting malicious headers or altering the legitimate ones.

2. Content-Type confusion: Incorrect MIME types may lead to response content being interpreted wrongly or mistakenly treated as a different format, increasing the risk of Cross-Site Scripting (XSS) attacks.

3. Cache poisoning: Attackers might exploit the vulnerability to poison the cache served by a web application, causing users to receive incorrect or malicious content while requesting resources.

- NVD - CVE-2025-1217
- PHP ChangeLog
- MITRE - CVE-2025-1217

To protect your web applications from potential exploitation, it's crucial to stay informed about newly discovered vulnerabilities and take appropriate actions. In the case of this specific vulnerability, upgrading PHP to versions 8.1.32, 8.2.28, 8.3.19, or 8.4.5 or higher is recommended. Stay safe, and keep your applications secure!

Timeline

Published on: 03/29/2025 06:15:36 UTC
Last modified on: 04/01/2025 20:26:30 UTC