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PatchSiren cyber security CVE debrief

CVE-2026-52747 owasp-modsecurity CVE debrief

CVE-2026-52747 is a high-severity vulnerability in ModSecurity, a web application firewall engine. The vulnerability allows attackers to bypass security rules by exploiting the multipart/form-data request body parser, which silently removes embedded line breaks from non-file form-field values. This parser differential can cause rules that inspect ARGS or ARGS_POST to miss payloads whose dangerous syntax depends on a line break. Affected users should upgrade to ModSecurity version 3.0.16 or later and review security rules to account for potential parser differentials.

Vendor
owasp-modsecurity
Product
ModSecurity
CVSS
HIGH 8.6
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-10
Original CVE updated
2026-07-10
Advisory published
2026-07-10
Advisory updated
2026-07-10

Who should care

Users of ModSecurity versions prior to 3.0.16 should be aware of this vulnerability and take steps to mitigate it. This includes reviewing and updating security rules to account for potential parser differentials and monitoring for suspicious activity. Operators, platform administrators, vulnerability management teams, and security teams should review the official advisory and CVE record to validate affected scope, severity, and vendor guidance.

Technical summary

The multipart/form-data request body parser in ModSecurity versions prior to 3.0.16 silently removes embedded line breaks from non-file form-field values before exporting them to ARGS and ARGS_POST. This creates a parser differential between ModSecurity and backend applications that preserve line breaks in form fields, allowing rules that inspect ARGS or ARGS_POST to miss payloads whose dangerous syntax depends on a line break. The vulnerability is fixed in version 3.0.16.

Defensive priority

High

Recommended defensive actions

  • Upgrade to ModSecurity version 3.0.16 or later
  • Review and update security rules to account for potential parser differentials
  • Monitor for suspicious activity and adjust logging and alerting as needed
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record was published on 2026-07-10T22:16:42.697Z and has not been modified since then. The NVD entry is currently 8.6 HIGH. This vulnerability affects ModSecurity versions prior to 3.0.16. The multipart/form-data request body parser in ModSecurity silently removes embedded line breaks from non-file form-field values before exporting them to ARGS and ARGS_POST. Users should verify their deployments and review official advisories for affected scope and vendor guidance.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-10T22:16:42.697Z and has not been modified since then.