CVE-2020-5268

Subject Confirmation Method not validated in Saml2 Authentication Services for ASP.NET

HIGH
7.3
CVSS Score
Published: April 21, 2020 at 03:30 PM UTC
Updated: June 17, 2026 at 03:21 AM UTC
1 product affected across 1 vendorSaml2

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Severity
HIGH7.3
Exploit prediction
EPSS 1%

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v ≤ 2.6.0v < 1.0.22.0.0 ≤ v < 2.7.0
Affected range stops below 1.0.2, so it looks safe — our inference, not a vendor statement
Affected range stops below 2.7.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-303CWE-287

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