CVE-2026-61813: Cert Validation Flaw (CVSS 3.7)

Description

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Prior to 2.9.15 and 3.0.17, the HttpsClient::download function in src/utils/https_client.cc sets libcurl CURLOPT_SSL_VERIFYHOST to 1 instead of the strict value 2L. Under adversary-in-the-middle and TLS interception conditions, this non-strict setting may weaken TLS peer identity validation and increase the risk of accepting a certificate for an unintended host. End-to-end exploitation is non-trivial in typical environments. This issue is fixed in versions 2.9.15 and 3.0.17.

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CVSS v3.1 Score

3.7

LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS — Exploit Prediction

0.0016

Probability of exploitation

0.05%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-295 CWE-295

References

Other References

https://github.com/owasp-modsecurity/ModSecurity/commit/cce204806430e4848327aadeb9113e654631a0c1 https://github.com/owasp-modsecurity/ModSecurity/commit/edca70d853bfb725325137fa40d178beebc324fc https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v2.9.15 https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.17 https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-2vqc-36qp-ccmw

Frequently Asked Questions

What is CVE-2026-61813? +

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Prior to 2.9.15 and 3.0.17, the HttpsClient::download function in src/utils/https_client.cc sets libcurl CURLOPT_SSL_VERIFYHOST to 1 instead of the strict value 2L. Under adversary-in-the-middle and TLS interception conditions, this non-strict setting may weaken TLS peer identity validation and increase the risk of accepting a certificate for an unintended host. End-to-end exploitation is non-trivial in typical environments. This issue is fixed in versions 2.9.15 and 3.0.17. It has a CVSS v3.1 base score of 3.7 (LOW).

How severe is CVE-2026-61813? +

CVE-2026-61813 has a CVSS v3.1 score of 3.7 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0016, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-61813? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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