CVE-2020-5268 Subject Confirmation Method not validated in Saml2 Authentication Services for ASP.NET
Attackers can bypass authentication by using SAML2 tokens with non-bearer confirmation methods, allowing unauthorized session creation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2020-5268?
CVE-2020-5268 is a medium-severity authentication bypass vulnerability in Sustainsys Saml2, published on 21 Apr 2020. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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.
Which versions are affected by CVE-2020-5268?
4 open source packages ship an affected version, including Sustainsys.Saml2. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
Sustainsys.Saml2 NuGet | All versions | 1.0.2 |
Sustainsys.Saml2 NuGet | All versions | 1.0.2 |
Sustainsys.Saml2 NuGet | From 2.0.0 | 2.7.0 |
Sustainsys.Saml2 NuGet | From 2.0.0 | 2.7.0 |
Products include Sustainsys Saml2.
How do I fix CVE-2020-5268?
Upgrade Sustainsys.Saml2 to a fixed version for your release line: 1.0.2 or 2.7.0.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2020-5268 being exploited?
There is no known exploitation of CVE-2020-5268 in the wild and no public exploit code.
Other vulnerabilities in Sustainsys Saml2
Sources
Also known as GHSA-9475-xg6m-j7pw.