Overview
This report covers an important vulnerability, identified as CVE-2025-48866, that affects ModSecurity, an open-source, cross-platform web application firewall engine for Apache, IIS, and Nginx. The vulnerability can lead to a denial of service, potentially compromising systems or leading to data leaks. It is critical for organizations using ModSecurity to understand and address this vulnerability to protect their systems and data.
Vulnerability Summary
CVE ID: CVE-2025-48866
Severity: High (7.5 CVSS v3 Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Denial of Service and potential system compromise or data leakage
Affected Products
Escape the Surveillance Era
Most apps won’t tell you the truth.
They’re part of the problem.
Phone numbers. Emails. Profiles. Logs.
It’s all fuel for surveillance.
Ameeba Chat gives you a way out.
- • No phone number
- • No email
- • No personal info
- • Anonymous aliases
- • End-to-end encrypted
Chat without a trace.
Product | Affected Versions
ModSecurity for Apache | < 2.9.10 ModSecurity for IIS | < 2.9.10 ModSecurity for Nginx | < 2.9.10 How the Exploit Works
The vulnerability exists within the `sanitiseArg` alias `sanitizeArg` actions of ModSecurity. An attacker can submit a large number of arguments in an HTTP request, which ModSecurity fails to handle properly. This results in a denial of service due to resource exhaustion. The same flaw can potentially be leveraged to compromise the system or leak data.
Conceptual Example Code
Here’s a conceptual example of a HTTP request that exploits the vulnerability:
POST /vulnerable/endpoint HTTP/1.1
Host: target.example.com
Content-Type: application/x-www-form-urlencoded
arg1=value&arg2=value&arg3=value&arg4=value&...&argN=valueIn the above example, ‘argN’ represents an excessive number of arguments that exploit the vulnerability.
Mitigation Guidance
The recommended mitigation is to upgrade to ModSecurity version 2.9.10 or later, which has a fix for this specific vulnerability. If upgrading is not immediately possible, a temporary workaround is to avoid using rules that contain the `sanitiseArg` or `sanitizeArg` action. Utilizing a web application firewall (WAF) or intrusion detection system (IDS) can also provide temporary mitigation.
