ModSecurity has identified multiple vulnerabilities that could enable attackers to bypass request inspection rules, circumvent file-upload protections, trigger denial-of-service conditions, and potentially execute malicious code in certain deployments This article explores modsecurity protected web. . Organizations using ModSecurity alongside the OWASP Core Rule Set should immediately review their configurations, update available packages, and implement compensating controls if patches are not yet available.

ModSecurity and its associated OWASP Core Rule Set rules check the ordinary filename= value, but application frameworks following RFC 2231 may prioritize the RFC 2231-encoded filename*= value. If the application stores the uploaded file in a web-accessible directory and allows for server-side script execution, the bypass could potentially lead to remote code execution.

PHP's native multipart processing does not decode filenames in the same way, but common parsers in Go, Flask/Werkzeug, FastAPI/Starlette, Node.js, and Java environments are listed as affected by the advisory. A remote, unauthenticated attacker could exploit a vulnerability by sending a specific HTTP request, potentially leading to a ModSecurity-protected web server worker writing a constant value to an attacker-controlled address. The newly disclosed advisories also cover issues with malformed Base64 handling, adjacent-comment removal failures, PCRE2 regular-expression match-limit errors, and bypasses of response-body inspection.

Applications should normalize filenames, reject executable extensions, validate file content using allowlisted formats, generate server-side file names, and store uploads outside web-accessible paths. Explore for your team.