Overview
CVE-2025-66373 describes a HTTP request smuggling vulnerability affecting Akamai Ghost on Akamai CDN edge servers before version 2025-11-17. This vulnerability arises from an error in processing chunked request bodies. When Akamai Ghost encounters an invalid chunked body (where the declared chunk size doesn’t match the actual chunk data size), it may, under specific circumstances, forward the invalid request, along with superfluous bytes, to the origin server. These superfluous bytes can potentially be used to smuggle malicious HTTP requests.
The exploitability of this vulnerability is heavily dependent on the origin server’s behavior and how it processes the invalid request it receives from Akamai Ghost. Origin servers must be carefully configured to properly validate incoming requests.
Technical Details
The vulnerability lies in Akamai Ghost’s handling of HTTP chunked encoding. HTTP chunked encoding is a transfer encoding mechanism that allows web servers to send HTTP responses in a series of chunks. Each chunk is preceded by its size in hexadecimal notation. If a client crafts a request with a malformed chunk size (e.g., a size larger than the actual data being sent), Akamai Ghost may incorrectly forward this request, including any subsequent data, to the origin server. The extraneous data following the malformed chunk represents the potential for smuggled requests.
Specifically, the issue stems from a discrepancy between the declared chunk size and the actual data received. Akamai Ghost fails to adequately validate this, allowing attackers to insert malicious requests within the invalid chunked data.
CVSS Analysis
Currently, a CVSS score for CVE-2025-66373 is unavailable (N/A). A CVSS score will depend on factors such as attack complexity, scope, confidentiality impact, integrity impact, and availability impact. This score is heavily dependent on the configuration of the Akamai CDN implementation and the backend origin server’s vulnerability to request smuggling attacks. Without a CVSS score, it’s important to prioritize this based on potential impact to the backend.
Possible Impact
The potential impact of this vulnerability depends on the origin server’s susceptibility to HTTP request smuggling. Successful exploitation could lead to:
- Data Exposure: An attacker could potentially intercept or modify sensitive data being transmitted between the client and the origin server.
- Account Hijacking: In some cases, an attacker might be able to hijack user accounts by manipulating requests.
- Cache Poisoning: The attacker could manipulate cached responses to serve malicious content to other users.
- Denial of Service (DoS): An attacker might be able to cause the origin server to become overloaded or crash.
The severity of the impact is highly dependent on the origin server’s architecture and security measures.
Mitigation and Patch Steps
Akamai has addressed this vulnerability in Ghost versions released after 2025-11-17. The following steps should be taken to mitigate the risk:
- Upgrade Akamai Ghost: Ensure your Akamai CDN is running a version of Ghost patched against CVE-2025-66373 (version released on or after 2025-11-17).
- Origin Server Hardening: Implement robust HTTP request validation on the origin server. This includes:
- Strictly parsing and validating HTTP headers.
- Properly handling malformed or unexpected requests.
- Enforcing consistent request handling across all server components.
- Web Application Firewall (WAF): Deploy a WAF to detect and block suspicious HTTP requests, including those attempting to exploit request smuggling vulnerabilities.
- Regular Security Audits: Conduct regular security audits and penetration testing to identify and address potential vulnerabilities in your Akamai CDN configuration and origin server.
