CVE-2026-57175: social-auth-core has an Improper Authentication issue
Impact
The SAML backend accepted SAML responses on the Assertion Consumer Service endpoint without verifying that they matched a previously issued AuthnRequest.
Applications using SAML account association could allow an attacker with a valid account on a trusted IdP to link the attacker's SAML identity to a logged-in victim's local account. The attacker could then authenticate through SAML and gain access to the victim's account.
The issue affects applications using the SAML backend together with authenticated account association.
Patches
The issue has been fixed by validating SAML responses against stored AuthnRequest IDs.
Users should upgrade to a patched version.
Fix:
https://github.com/python-social-auth/social-core/pull/1794
Workarounds
Applications that cannot upgrade immediately should disable SAML account association for already authenticated users.
If SAML login is not required, the SAML backend can also be disabled by removing it from SOCIALAUTHAUTHENTICATIONBACKENDS.
There is no complete workaround while continuing to allow vulnerable SAML account association.
Credits
Reported through GitHub private vulnerability reporting by Liyi Zhou, Ziyue Wang, Strick, Maurice, and Chenchen Yu from the University of Sydney security research team.
Reporter references:
https://lzhou1110.github.io/ https://zyy0530.github.io/ https://str1ckl4nd.github.io/ https://maurice.busystar.org/ https://7thparkk.github.io/
Other sources
Python Social Auth is a social authentication/registration mechanism. Prior to version 5.0.0, the SAML backend accepted SAML responses on the Assertion Consumer Service endpoint without verifying that they matched a previously issued AuthnRequest. Applications using SAML account association could allow an attacker with a valid account on a trusted IdP to link the attacker's SAML identity to a logged-in victim's local account. The attacker could then authenticate through SAML and gain access to the victim's account. The issue affects applications using the SAML backend together with authenticated account association. The issue has been fixed in version 5.0.0 by validating SAML responses against stored AuthnRequest IDs.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/social-auth-coreto a version that resolves this vulnerability.Fixed in 5.0.0 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 5.0.0 - Configuration
Disable SAML account association for already authenticated users until the application can be upgraded.
SAML account association = disabled - Configuration
If SAML login is not required, disable the SAML backend by removing it from SOCIAL_AUTH_AUTHENTICATION_BACKENDS.
SOCIAL_AUTH_AUTHENTICATION_BACKENDS = SAML backend removed
Event History
Frequently Asked Questions
Which deployments are affected?
The issue affects applications that use the social-auth-core SAML backend together with authenticated account association. The vulnerable behavior is present before version 5.0.0.
What must an attacker be able to do to take over an account?
The attacker needs a valid account at a trusted identity provider and must be able to cause their SAML identity to be associated with a logged-in victim's local account. They can then authenticate through SAML as the victim.
What changed in the fixed release?
Version 5.0.0 validates SAML responses against stored AuthnRequest IDs, preventing acceptance of responses that do not match a previously issued authentication request.