CVE-2025-4366: Request Smuggling Vulnerability in Pingora’s Proxying Framework

Overview

The Common Vulnerabilities and Exposures (CVE) system has identified a critical vulnerability, designated as CVE-2025-4366, within Pingora’s proxying framework, pingora-proxy. This vulnerability has a significant impact on the security of any system using the affected software, as it could lead to unauthorized request execution and potential cache poisoning. The severity of this vulnerability, combined with the widespread use of Pingora’s proxying framework, makes it a critical issue for the cybersecurity community. It is crucial for organizations using Pingora’s proxying framework to understand and mitigate this vulnerability to protect their systems and data from potential attacks.

Vulnerability Summary

CVE ID: CVE-2025-4366
Severity: High (CVSS: 8.0)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise, Data leakage, Unauthorized request execution, Cache poisoning

Affected Products

Product | Affected Versions

Pingora’s Proxying Framework | All versions before the patch

How the Exploit Works

The exploit works via a request smuggling attack. An attacker manipulates the HTTP request bodies on cache HITs, injecting malicious HTTP requests into the communication between the client and the server. This leads to unauthorized request execution. The vulnerability also opens the door for potential cache poisoning. In an environment where Pingora’s proxying framework is used for caching, an attacker can manipulate headers and URLs in subsequent requests made on the same HTTP/1.1 connection.

Conceptual Example Code

Here is a conceptual example of how the vulnerability might be exploited:

POST /target/endpoint HTTP/1.1
Host: vulnerable.example.com
Content-Length: 100
Content-Type: text/plain
Transfer-Encoding: chunked
0
GET /internal/admin HTTP/1.1
Host: vulnerable.example.com
X-Ignore: X

In this example, the attacker is manipulating the ‘Content-Length’ and ‘Transfer-Encoding’ headers to smuggle a malicious request (GET /internal/admin) within the body of an initial benign request. The server interprets this as two separate requests and executes the malicious request, leading to unauthorized access.

Mitigation Measures

A patch for this vulnerability is available and can be accessed via the following GitHub commit: https://github.com/cloudflare/pingora/commit/fda3317ec822678564d641e7cf1c9b77ee3759ff. All users of Pingora’s proxying framework are strongly recommended to apply this patch immediately.
As a temporary mitigation measure, users can also use a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) to monitor and block potential request smuggling attacks. However, these measures cannot completely eliminate the threat and are not a substitute for patching the vulnerability.
It is essential for organizations to enforce a robust cybersecurity policy, including regular software updates and vulnerability assessments, to ensure the security of their systems and data.