CVE-2026-42268: ModSecurity Unsigned Integer Underflow Vulnerability
Summary
CVE-2026-42268: ModSecurity: Unsigned integer underflow in @verifySSN / @verifyCPF / @verifySVNR operators. Affects modsecurity versions >= 3.0.0, < 3.0.15. Fixed in 3.0.15. How to fix ↓
Also tracked for
- modsecurity2 · Bitnami
The same CVE-2026-42268 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
ModSecurity is an open-source web application firewall (WAF) engine designed to protect web applications from various attacks. It operates across multiple platforms, including Apache, IIS, and Nginx. The package is widely used for its ability to provide real-time monitoring and protection against common web vulnerabilities. However, certain operators within ModSecurity, specifically @verifySSN, @verifyCPF, and @verifySVNR, have been found to be susceptible to an unsigned integer underflow issue, which can lead to unhandled exceptions.
Vulnerability Detail
The vulnerability arises from an unhandled exception (std::out_of_range) that occurs when the user (administrator) utilizes any of the @verifySSN, @verifyCPF, or @verifySVNR operators in ModSecurity versions from 3.0.0 to before 3.0.15. This unsigned integer underflow can lead to unexpected behavior, potentially allowing attackers to exploit the system. The severity of this vulnerability is classified as high, with a CVSS score of 4.0, indicating a significant risk to applications utilizing affected versions of ModSecurity.
How To Fix
Minimum fixed version
3.0.15
This is the first release that contains the fix.
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Workaround
As a temporary workaround, administrators can avoid using the @verifySSN, @verifyCPF, or @verifySVNR operators in their ModSecurity rules until the package is updated to a secure version.
Conclusion
In summary, CVE-2026-42268 represents a significant vulnerability in ModSecurity that can lead to unhandled exceptions due to unsigned integer underflow. It is crucial for users of affected versions to update to version 3.0.15 or later to mitigate the risk. Additionally, temporary workarounds can be employed until the update is completed.
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FAQ
CVE-2026-42268 is a vulnerability in ModSecurity that involves an unsigned integer underflow in specific operators, leading to potential unhandled exceptions.
ModSecurity versions from 3.0.0 to before 3.0.15 are affected by this vulnerability.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
The vulnerability can lead to unhandled exceptions, which may allow attackers to exploit the system, potentially compromising the security of the web application.
To fix the issue, update ModSecurity to version 3.0.15 or later using your package manager, such as 'bitnami update modsecurity' for Bitnami installations.
References
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