CVE-2021-21239: Open default xmlsec1 key-type preference
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: Open an issue in pysaml2 Email us at the incident-response address
Other sources
PySAML2 is a pure python implementation of SAML Version 2 Standard. PySAML2 before 6.5.0 has an improper verification of cryptographic signature vulnerability. Users of pysaml2 that use the default CryptoBackendXmlSec1 backend and need to verify signed SAML documents are impacted. PySAML2 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. This is fixed in PySAML2 6.5.0.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2021-21239?
CVE-2021-21239 has a moderate severity level as it affects the verification of signed SAML documents in pysaml2.
How do I fix CVE-2021-21239?
To fix CVE-2021-21239, upgrade pysaml2 to version 6.5.0 or later.
What versions of pysaml2 are affected by CVE-2021-21239?
All versions of pysaml2 up to and including 6.4.1 are affected by CVE-2021-21239.
Who is impacted by CVE-2021-21239?
All users of pysaml2 that use the default CryptoBackendXmlSec1 backend and need to verify signed SAML documents are impacted.
What is the primary issue with CVE-2021-21239?
The primary issue with CVE-2021-21239 is that it does not ensure the correct signing of SAML documents.