CVE-2021-21238

Name: CVE-2021-21238
Creator: NVD / NIST
Published: 2021-01-21T15:15:14.11+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.08%

Last modified Jun 17, 2026

CVE-2021-21238 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. PySAML2 is a pure python implementation of SAML Version 2 Standard. PySAML2 before 6.5.0 has an improper verification of cryptographic signature vulnerability. EPSS estimates a 1.08% chance of exploitation in the next 30 days.

Description

PySAML2 is a pure python implementation of SAML Version 2 Standard. PySAML2 before 6.5.0 has an improper verification of cryptographic signature vulnerability. All users of pysaml2 that need to validate signed SAML documents are impacted. The vulnerability is a variant of XML Signature wrapping because it did not validate the SAML document against an XML schema. This allowed invalid XML documents to be processed and such a document can trick pysaml2 with a wrapped signature. This is fixed in PySAML2 6.5.0.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

EPSS Probability

1.08%

60.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-347

Affected Software

Vendor	Product	Versions
Pysaml2 Project	Pysaml2	< 6.5.0

References

https://github.com/IdentityPython/pysaml2/commit/1d8fd268f5bf887480a403a7a5ef8f048157cc14Patch, Third Party Advisory
https://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0Third Party Advisory
https://github.com/IdentityPython/pysaml2/security/advisories/GHSA-f4g9-h89h-jgv9Third Party Advisory
https://pypi.org/project/pysaml2Product, Third Party Advisory
https://github.com/IdentityPython/pysaml2/commit/1d8fd268f5bf887480a403a7a5ef8f048157cc14Patch, Third Party Advisory
https://github.com/IdentityPython/pysaml2/releases/tag/v6.5.0Third Party Advisory
https://github.com/IdentityPython/pysaml2/security/advisories/GHSA-f4g9-h89h-jgv9Third Party Advisory
https://pypi.org/project/pysaml2Product, Third Party Advisory

Timeline

Published: Jan 21, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21238?

How severe is CVE-2021-21238?

CVE-2021-21238 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.08% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21238?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21238?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST