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Date: May 6, 2020

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.

Language: C#

Severity Score

Severity Score

Weakness Type (CWE)

Authentication Issues


Top Fix


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Upgrade to version Sustainsys.Saml2:1.0.2,2.7.0

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CVSS v3.1

Base Score:
Attack Vector (AV): NETWORK
Attack Complexity (AC): LOW
Privileges Required (PR): LOW
User Interaction (UI): REQUIRED
Confidentiality (C): HIGH
Integrity (I): HIGH
Availability (A): NONE


Base Score:
Access Vector (AV): NETWORK
Access Complexity (AC): MEDIUM
Authentication (AU): SINGLE
Confidentiality (C): PARTIAL
Integrity (I): PARTIAL
Availability (A): NONE
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