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Improper Verification of Cryptographic Signature in PySAML2

Moderate severity GitHub Reviewed Published Jan 20, 2021 in IdentityPython/pysaml2 • Updated Feb 3, 2023

Package

pip pysaml2 (pip)

Affected versions

< 6.5.0

Patched versions

6.5.0

Description

Impact

All users of pysaml2 that use the default CryptoBackendXmlSec1 backend and need to verify signed SAML documents are impacted. pysaml2 <= 6.4.1 does not ensure that a signed SAML document is correctly signed. The default CryptoBackendXmlSec1 backend is using the xmlsec1 binary to verify the signature of signed SAML documents, but by default, xmlsec1 accepts any type of key found within the given document. xmlsec1 needs to be configured explicitly to only use only x509 certificates for the verification process of the SAML document signature.

Patches

Users should upgrade to pysaml2 v6.5.0.

Workarounds

No workaround provided at this point.

References

This issue has been reported in the past at the xmlsec1 mailing list:
https://www.aleksey.com/pipermail/xmlsec/2013/009717.html

Credits

  • Brian Wolff

For more information

If you have any questions or comments about this advisory:

References

@c00kiemon5ter c00kiemon5ter published to IdentityPython/pysaml2 Jan 20, 2021
Reviewed Jan 21, 2021
Published to the GitHub Advisory Database Jan 21, 2021
Published by the National Vulnerability Database Jan 21, 2021
Last updated Feb 3, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

EPSS score

0.202%
(58th percentile)

Weaknesses

CVE ID

CVE-2021-21239

GHSA ID

GHSA-5p3x-r448-pc62

Source code

Credits

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