ModSecurity Patches Two High-Severity Flaws Allowing WAF Bypass and Potential Remote Code Execution
ModSecurity patches two high-severity flaws enabling WAF bypass and potential RCE.
ModSecurity, an open-source WAF, has disclosed two high-severity vulnerabilities. The first allows for malicious file uploads and bypasses WAF checks due to improper handling of RFC 2231 encoded filenames, potentially leading to remote code execution in applications using Go, Python, Node.js, and Java Spring. The second vulnerability, related to XML argument parsing, can cause server crashes or RCE when a specific configuration is enabled. While a patch is mentioned for the XML flaw, it's not yet released, and no patch is available for the filename issue, urging developers to implement application-level security measures.
AI summary of the linked source. Not reviewed by an editor. How this works
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The lesson from this incident
Full lessonTwo high-severity vulnerabilities in ModSecurity—a widely deployed open-source Web Application Firewall—expose applications to WAF bypass via malformed RFC 2231 encoded filenames and potential remote code execution through malicious XML argument parsing. The filename handling flaw is particularly dangerous because it undermines the core purpose of a WAF: inspecting and blocking malicious inputs before they reach the application. What makes this especially critical is that patches are either incomplete or entirely unavailable, leaving organizations reliant on compensating controls. This incident highlights the inherent risk of depending on a single security control, especially when that control itself contains unpatched vulnerabilities.
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Indicators of Compromise
Extracted by AI from the linked source. Not reviewed by an editor. How this works
- cve — CVE-2026-104269
- cve — CVE-2026-73857
- mitre_attack — T1078
- mitre_attack — T1505