PySAML2 before 5.0.0 does not check that the signature in a SAML document is enveloped and thus signature wrapping is effective, i.e., it is affected by XML Signature Wrapping (XSW). The signature information and the node/object that is signed can be in different places and thus the signature verification will succeed, but the wrong data will be used. This specifically affects the verification of assertion that have been signed.
References and upstream commits:
Created python-pysaml2 tracking bugs for this issue:
Affects: fedora-all [bug 1794741]
Affects: openstack-rdo [bug 1794742]
All versions of Red Hat OpenStack Platform ship but do not use the flawed check-signature functionality of python-pysaml2. The impact for these products is therefore rated as having a security impact of Low.
There is no known mitigation for this issue, the flaw can only be resolved by applying updates.