CVE-2026-41670: Input Validation Flaw (CVSS 8.2)

Description

Admidio is an open-source user management solution. Prior to version 5.0.9, the SAML IdP implementation in Admidio's SSO module uses the AssertionConsumerServiceURL value directly from incoming SAML AuthnRequest messages as the destination for the SAML response, without validating it against the registered ACS URL (smc_acs_url) stored in the database for the corresponding service provider client. An attacker who knows the Entity ID of a registered SP client can craft a SAML AuthnRequest with an arbitrary AssertionConsumerServiceURL, causing the IdP to send the signed SAML response -- containing user identity attributes (login name, email, roles, profile fields) -- to an attacker-controlled URL. This issue has been patched in version 5.0.9.

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CVSS v3.1 Score

8.2

HIGH

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

EPSS — Exploit Prediction

0.0002

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-20 Improper Input Validation

CWE-601 CWE-601

References

Other References

https://github.com/Admidio/admidio/releases/tag/v5.0.9 https://github.com/Admidio/admidio/security/advisories/GHSA-p9w9-87c8-m235 https://github.com/Admidio/admidio/security/advisories/GHSA-p9w9-87c8-m235

Frequently Asked Questions

What is CVE-2026-41670? +

Admidio is an open-source user management solution. Prior to version 5.0.9, the SAML IdP implementation in Admidio's SSO module uses the AssertionConsumerServiceURL value directly from incoming SAML AuthnRequest messages as the destination for the SAML response, without validating it against the registered ACS URL (smc_acs_url) stored in the database for the corresponding service provider client. An attacker who knows the Entity ID of a registered SP client can craft a SAML AuthnRequest with an arbitrary AssertionConsumerServiceURL, causing the IdP to send the signed SAML response -- containing user identity attributes (login name, email, roles, profile fields) -- to an attacker-controlled URL. This issue has been patched in version 5.0.9. It has a CVSS v3.1 base score of 8.2 (HIGH).

How severe is CVE-2026-41670? +

CVE-2026-41670 has a CVSS v3.1 score of 8.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-41670? +

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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