Auth bypass in Sustainsys Saml2
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 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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:L/A:N.
EPSS exploit prediction
EPSS: 0.011 (63.9th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 64th percentile — 63.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: 0.000
Affected products
- Sustainsys Saml2 — versions < 1.0.2, >= 2.0.0, <= 2.6.0
Weakness classification (CWE)
References
- github.com/Sustainsys/Saml2/commit/e58e0a1aff2b1ead6aca080b7cdced55ee6d5241 (Patch, Third Party Advisory)
- github.com/Sustainsys/Saml2/security/advisories/GHSA-9475-xg6m-j7pw (Third Party Advisory, Mitigation)
- github.com/Sustainsys/Saml2/issues/712 (Third Party Advisory)
- www.nuget.org/packages/Sustainsys.Saml2/ (Third Party Advisory)
Frequently asked questions
- What is CVE-2020-5268?
- CVE-2020-5268 is a medium-severity vulnerability in Sustainsys Saml2, classified under Incorrect Implementation of Authentication Algorithm. CVSS score: 6.5/10. Published 2020-04-21.
- How severe is CVE-2020-5268?
- Medium severity. CVSS v3 base score is 6.5 out of 10.