CVE-2020-5268: In Saml2 Authentication Services for ASP.NET versions before 1.0.2, and between 2.0.0 and 2.6.0, there is a vulnerability in how tokens are validated in some ca

In Saml2 Authentication Services for ASP.NET versions before 1.0.2, and between 2.0.0 and 2.6.0, there is a vulnerability in how tokens are validated in some ca

In Saml2 Authentication Services for ASP.NET versions before 1.0.2, and between 2.0.0 and 2.6.0, there is a vulnerability in how tokens are validated in some cases. Saml2 tokens are usually used as bearer tokens - a caller that presents a token is assumed to be the subject of the token. There is also support in the Saml2 protocol for issuing tokens that is tied to a subject through other means, e.g. holder-of-key where possession of a private key must be proved. The Sustainsys.Saml2 library incorrectly treats all incoming tokens as bearer tokens, even though they have another subject confirmation method specified. This could be used by an attacker that could get access to Saml2 tokens with another subject confirmation method than bearer. The attacker could then use such a token to create a log in session. This vulnerability is patched in versions 1.0.2 and 2.7.0.

Description from the National Vulnerability Database, published by GitHub

What it means for a small business

If your business uses Saml2, install the vendor's update. If you're not sure whether you use it, ask whoever manages your computers.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 1.1%, higher than 65% of CVEs. That’s above average: worth scheduling this week. Scored October 29, 2026, updated daily.

Check your own setup

Website check: reads what your site runs from the outside (WordPress version, plugins it can see, old server software) and matches it against this database.
Server check: what your web server says about itself, and whether that version has known flaws.

Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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