CVE-2020-5261Network attack vector

Authentication bypass via disabled assertion replay validation

Published Mar 25, 2020 · Updated Aug 4, 2024

Authentication bypass in Sustainsys.Saml2 2.0.0 through 2.4.0 allows remote authenticated users to reuse captured SAML assertions. Saml2Response did not enable replay validation, and the token handler's workaround reserialized assertions in a form that failed when optional fields were absent. Possession of a still-valid signed assertion is required; replay grants that assertion's authenticated privileges without interrupting service.

CVSS severity8.2
High
EPSS probability1.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Sustainsys.Saml2 2.0.0 through 2.4.0 allows remote authenticated users to reuse captured SAML assertions. Saml2Response did not enable replay validation, and the token handler's workaround reserialized assertions in a form that failed when optional fields were absent. Possession of a still-valid signed assertion is required; replay grants that assertion's authenticated privileges without interrupting service.

The record

CVE
CVE-2020-5261
Published
Mar 25, 2020
Updated
Aug 4, 2024
Vendor
Sustainsys
Product
Sustainsys.Saml2
Classifications
CWE-294, CAPEC-60, T1550
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 25, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 2.0.0, < 2.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Sustainsys · Sustainsys.Saml2version=>= 2.0.0, < 2.5.0

Published CVSS scores

6.8NIST NVDCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
8.2GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N
4.9NIST NVDAV:N/AC:M/Au:S/C:P/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-294Authentication Bypass by Capture-replay
CAPEC-60Reusing Session IDs (aka Session Replay)
T1550Use Alternate Authentication Material

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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