Missing Token Replay Detection
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- High
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-294.
Summary
Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 has a faulty implementation of Token Replay Detection. Token Replay Detection is an important defence in depth measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 is not affected. It has a correct Token Replay Implementation and is safe to use. Saml2 Authentication services for ASP.NET (NuGet package Sustainsys.Saml2) greater than 2.0.0, and less than version 2.5.0 have a faulty implementation of Token Replay Detection. Token Replay Detection is an important defense measure for Single Sign On solutions. The 2.5.0 version is patched. Note that version 1.0.1 and prior versions are not affected. These versions have a correct Token Replay Implementation and are safe to use.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Sustainsys | Saml2 | 2.0.0 to before 2.5.0 | 2.5.0 | Patch available | CNA |
| — | Sustainsys.Saml2 (NuGet) | 2.0.0 to before 2.5.0 | 2.5.0 | Patch available | GHSA-g6j2-ch25-5mmv |
- Saml2 VendorSustainsys Affected 2.0.0 to before 2.5.0 Fixed in 2.5.0 Patch available CNA
- Sustainsys.Saml2 (NuGet) Vendor— Affected 2.0.0 to before 2.5.0 Fixed in 2.5.0 Patch available GHSA-g6j2-ch25-5mmv
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:sustainsys:saml2:*:*:*:*:*:*:*:* | 2.0.0 to before 2.5.0 | Vulnerable | Sustainsys |
- cpe:2.3:a:sustainsys:saml2:*:*:*:*:*:*:*:* Versions 2.0.0 to before 2.5.0 Vulnerable ·Sustainsys
Remediation
- Fix · CNA Saml2 (Sustainsys) Fixed in 2.5.0
- Fix · GHSA-g6j2-ch25-5mmv Sustainsys.Saml2 (NuGet) Fixed in 2.5.0 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2020-5261
- 2026-10-03 Alias added: GHSA-g6j2-ch25-5mmv
References
More Sustainsys Saml2 vulnerabilities
- TI-2023-22282 Sustainsys.Saml2 Insufficient Identity Provider Issuer Validation CVSS 3.1HIGH 7.5
- TI-2020-04324 Subject Confirmation Method not validated in Saml2 Authentication Services for ASP.NET CVSS 3.1HIGH 7.3
Sources
- CVE-2020-5261 · CVE Program
- CVE-2020-5261 · NVD
- FIRST EPSS
- GHSA-g6j2-ch25-5mmv · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences