CVE-2026-27613

Comprehensive Technical Analysis of CVE-2026-27613

1. Vulnerability Assessment and Severity Evaluation

CVE ID: CVE-2026-27613 CVSS Score: 9.8

The vulnerability in TinyWeb, a web server written in Delphi for Win32, allows unauthenticated remote attackers to bypass the web server's CGI parameter security controls. This vulnerability is severe, as indicated by its high CVSS score of 9.8. The potential impacts include source code disclosure and remote code execution (RCE), which can lead to significant security breaches.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• Unauthenticated Remote Access: Attackers can exploit this vulnerability without needing any authentication, making it highly accessible.
• CGI Parameter Manipulation: The primary attack vector involves manipulating CGI parameters to bypass security controls.

Exploitation Methods:

• Source Code Disclosure: By manipulating CGI parameters, attackers can potentially access and disclose the source code of the web application.
• Remote Code Execution (RCE): Depending on the server configuration and the specific CGI executable in use, attackers can execute arbitrary code on the server. This is particularly dangerous if the server is running interpreted languages like PHP.

3. Affected Systems and Software Versions

Affected Software:

• TinyWeb versions prior to 2.01

Affected Systems:

• Systems running vulnerable versions of TinyWeb, particularly those hosting CGI scripts, especially in interpreted languages like PHP.

4. Recommended Mitigation Strategies

Immediate Mitigation:

• Upgrade to Version 2.01: The vulnerability has been patched in TinyWeb version 2.01. Upgrading to this version is the most effective mitigation strategy.
• Enable STRICT_CGI_PARAMS: If upgrading is not immediately possible, ensure that STRICT_CGI_PARAMS is enabled. This setting is defined by default in define.inc.
• Avoid Dangerous CGI Executables: Do not use CGI executables that natively accept dangerous command-line flags, such as php-cgi.exe.

Additional Mitigation:

• Web Application Firewall (WAF): If hosting PHP, consider placing the server behind a WAF that explicitly blocks URL query string parameters that begin with a hyphen (-) or contain encoded double quotes (%22).

5. Impact on Cybersecurity Landscape

The discovery and exploitation of this vulnerability highlight the ongoing risks associated with web server software, particularly those that handle CGI scripts. The potential for RCE and source code disclosure underscores the need for robust security practices, including regular updates, strict parameter handling, and the use of WAFs. This vulnerability serves as a reminder for organizations to prioritize security in their web server configurations and to stay vigilant about emerging threats.

6. Technical Details for Security Professionals

Vulnerability Details:

• The vulnerability stems from inadequate validation of CGI parameters, allowing attackers to bypass security controls.
• The impact varies based on server configuration and the specific CGI executable in use.

Patch Information:

• The issue has been addressed in TinyWeb version 2.01. The patch can be found in the commit d9dbda8db49da69d2160e1c527e782b73b5ffb6b.

References:

• Release Notes for TinyWeb v2.01
• Vendor Advisory
• Third Party Advisory

Conclusion: Security professionals should prioritize the upgrade to TinyWeb version 2.01 and implement the recommended mitigation strategies to protect against this critical vulnerability. Continuous monitoring and regular security audits are essential to identify and mitigate similar threats in the future.