Overview
A critical vulnerability has surfaced in LinuxServer.io heimdall version 2.6.3-ls307, which has potentially severe implications for the integrity and trustworthiness of the affected applications. The vulnerability, coined as CVE-2025-50578, is significant due to how it handles user-supplied HTTP headers. Specifically, it concerns the `X-Forwarded-Host` and `Referer` headers.
This vulnerability has been found exploitable by unauthenticated remote attackers who can manipulate these headers to perform Host Header Injection and Open Redirect attacks. These attacks may result in loading of external resources from attacker-controlled domains and unintended redirection of users, enabling phishing, UI redress, and session theft.
Vulnerability Summary
CVE ID: CVE-2025-50578
Severity: Critical (CVSS: 9.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise, data leakage, and unintended user redirection
Affected Products
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Product | Affected Versions
LinuxServer.io Heimdall | 2.6.3-ls307
How the Exploit Works
The vulnerability exists due to insufficient validation and trust of untrusted input, particularly HTTP headers such as `X-Forwarded-Host` and `Referer`. These headers can be manipulated by an unauthenticated remote attacker to perform Host Header Injection and Open Redirect attacks.
Host Header Injection allows an attacker to control the data that is returned to the user, potentially leading to a phishing attack. Open Redirect, on the other hand, could lead to the redirection of users to unintended, potentially malicious websites, thus enabling further attacks like phishing and session theft.
Conceptual Example Code
The following conceptual HTTP request demonstrates how an attacker might exploit this vulnerability:
GET / HTTP/1.1
Host: legitimatesite.com
X-Forwarded-Host: malicious.com
Referer: legitimatesite.comIn this example, the attacker manipulates the `X-Forwarded-Host` and `Referer` headers to point to a malicious domain, which could then serve inappropriate content or even capture sensitive user data.
Mitigation
The best mitigation for this vulnerability is to apply the vendor patch as soon as it becomes available. In the absence of a patch, or until one can be applied, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be used as temporary mitigation. These tools can be configured to block or alert on attempts to exploit this vulnerability by monitoring for suspicious manipulation of HTTP headers.