No exploitation reportedFix available

CVE-2020-5261

Q: Is CVE-2020-5261 actively exploited?

Active exploitation of CVE-2020-5261 has not been confirmed. Its EPSS score was 1.5% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2020-5261?

CVE-2020-5261 has a CVSS v3 base score of 6.8 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N.

No exploitation reported by the sources we read.

Published2020-03-25
Fixed in2.5.0
WeaknessCWE-294

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC

2020-03-2502:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-5261?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-5261?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV

Sustainsys saml2

Branch	Affected	Fixed in	Source
2.x	≥ 2.0.0, < 2.5.0	2.5.0	NVD · OSV

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Sustainsys saml2 to 2.5.0

Advisories and patches

github.comPatch

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CNACVSS 3.18.2read 2026-10-23
NVDCVSS 3.16.8read 2026-10-23
NVDCVSS 2.04.9read 2026-10-23
CNAweakness (CWE)CWE-294read 2026-10-23
NVDweakness (CWE)CWE-294read 2026-10-23
FIRST EPSSEPSS score1.5 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Published: 2020-03-25
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2020-5261?

Is CVE-2020-5261 actively exploited?

Active exploitation of CVE-2020-5261 has not been confirmed. Its EPSS score was 1.5% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-5261?

CVE-2020-5261 has a CVSS v3 base score of 6.8 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N.

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