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

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 validate the SAML document against an XML schema. This allows invalid XML documents to trick the verification process, by presenting elements with a valid signature inside elements whose content has been malformed. The verification is offloaded to xmlsec1 and xmlsec1 will not validate every signature in the given document, but only the first it finds in the given scope.

Patches

Users should upgrade to pysaml2 v6.5.0.

Workarounds

No workaround provided at this point.

References

No references provided at this point.

Credits

- Victor Schönfelder Garcia (isits AG International School of IT Security) - Juraj Somorovsky (Paderborn University) - Vladislav Mladenov (Ruhr University Bochum)

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

Last updated 25 August 2025

pysaml2 version 4.4.0 and older accept any password when run with python optimizations enabled. This allows attackers to log in as any user without knowing their password.

Python package pysaml2 version 4.4.0 and earlier reuses the initialization vector across encryptions in the IDP server, resulting in weak encryption of data.

It was found that python-pysaml2 is vulnerable to an XML external entity attack. python-pysaml2 does not sanitize SAML XML requests or responses.

References:

http://seclists.org/oss-sec/2017/q1/50 https://bugs.debian.org/850716

Upstream bug:

https://github.com/rohe/pysaml2/issues/366

Proposed patch (! actually fixes Bug 1415710):

https://github.com/rohe/pysaml2/pull/379

An entity expansion vulnerability was found in python-pysaml2.

Upstream patch:

https://github.com/rohe/pysaml2/commit/6e09a25d9b4b7aa7a506853210a9a14100b8bc9b

References:

http://seclists.org/oss-sec/2017/q1/140