Vulnerability in ModSecurity Web Application Firewall Engine
CVE-2026-52747

8.6HIGH

Key Information:

Vendor: Owasp-modsecurity
Status: Modsecurity
Vendor: CVE Published:; 10 July 2026

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What is CVE-2026-52747?

CVE-2026-52747 is a vulnerability found in ModSecurity, an open-source web application firewall (WAF) engine developed for integration with web servers such as Apache, IIS, and Nginx. ModSecurity serves to protect web applications by monitoring and filtering HTTP traffic, which helps safeguard against malicious requests and attacks. The vulnerability specifically resides in the multipart/form-data request body parser, present in versions prior to 3.0.16, where it inadequately handles embedded line breaks. This oversight can result in the removal of crucial line breaks from non-file form-field values, leading to a discrepancy between the data processed by ModSecurity and that preserved by backend applications. Consequently, security rules that check the ARGS and ARGS_POST variables could fail to detect potentially harmful payloads that rely on such line breaks, thereby jeopardizing the security of web applications that utilize ModSecurity.

Potential Impact of CVE-2026-52747

Evaded Security Measures: The failure to accurately process embedded line breaks means that malicious payloads could slip past the WAF without triggering alerts or detection. This evasion can allow attackers to execute harmful actions without being flagged by the security monitoring in place.
Increased Risk of Web Application Attacks: By exploiting this vulnerability, attackers could potentially inject harmful data into applications, which may lead to various types of attacks, such as cross-site scripting (XSS) or SQL injection, thereby compromising the integrity and confidentiality of sensitive information.
Compatibility Issues with Backend Systems: The inconsistency in how data is parsed and stored between ModSecurity and backend applications can lead to unforeseen errors and vulnerabilities in web functionalities. Such issues can disrupt application performance and reliability, causing further issues in web service delivery and user experience.