CVE-2026-42268 owasp-modsecurity CVE debrief

Who should care

Defenders and administrators using ModSecurity should assess their exposure and prioritize upgrading to version 3.0.15 or later. This includes reviewing ModSecurity version and rule configuration, and verifying potential security risks. Operators, platform administrators, and security teams should review the vulnerability and take necessary actions to mitigate the risk.

Why it matters

CVE-2026-42268 is a high-severity vulnerability in ModSecurity that can lead to potential DoS attacks and exploitation by attackers. Defenders and administrators should assess their exposure, verify ModSecurity version and rule configuration, and prioritize upgrading to version 3.0.15 or later.

• Potential denial-of-service (DoS) attacks
• Possible exploitation by attackers to bypass security controls
• Need for verification of ModSecurity version and rule configuration
• Priority for upgrading to fixed version 3.0.15

Technical summary

The vulnerability is caused by an unsigned integer underflow in libmodsecurity3, which can lead to an unhandled exception (std::out_of_range). This occurs when an administrator uses specific rules (@verifySSN, @verifyCPF, or @verifySVNR). The vulnerability affects ModSecurity versions from 3.0.0 to before 3.0.15 and is fixed in version 3.0.15. Defenders should prioritize upgrading to ModSecurity version 3.0.15 or later to mitigate this vulnerability. The vulnerability can lead to potential security risks and defenders should assess their exposure.

Defensive priority

Defenders should prioritize upgrading to ModSecurity version 3.0.15 or later to mitigate this vulnerability.

Recommended defensive actions

• Upgrade to ModSecurity version 3.0.15 or later
• Review and update ModSecurity rules to prevent exploitation
• Monitor ModSecurity logs for potential attacks
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The vulnerability is described in the CVE record and NVD vulnerability detail page. The issue is caused by an unsigned integer underflow in libmodsecurity3. The CVE record was published on 2026-05-12T22:16:34.337Z and has not been modified since then. The NVD vulnerability detail page provides additional information about the vulnerability. Defenders should verify ModSecurity version and rule configuration to assess their exposure.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.