CVE-2026-57179: social-auth-core has a Session Fixation issue
Impact
The partial-pipeline resume mechanism accepted partialtoken as a bearer credential without binding it to the browser session that created it.
Applications using resumable partial pipeline steps could allow an attacker to start an authentication flow, obtain a valid partial token and verification data, and cause a victim's browser to resume that attacker-controlled flow. This could authenticate the victim's browser as the attacker's account.
The issue affects applications using partial pipeline steps such as mailvalidation or custom steps decorated with @partial.
Patches
The issue has been fixed by binding partial pipeline resumes to the originating browser session.
Users should upgrade to a patched version.
Fix:
https://github.com/python-social-auth/social-core/pull/1816 https://github.com/python-social-auth/social-docs/pull/444 https://github.com/python-social-auth/social-app-django/pull/1009
Workarounds
Applications that cannot upgrade immediately should disable resumable partial pipeline steps, including mailvalidation and custom steps decorated with @partial.
If those flows are required, applications should avoid accepting partial resume links from untrusted contexts until a patched version can be deployed.
There is no complete workaround while continuing to use the vulnerable partial-pipeline resume mechanism.
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 partial-pipeline resume mechanism accepted partialtoken as a bearer credential without binding it to the browser session that created it. Applications using resumable partial pipeline steps could allow an attacker to start an authentication flow, obtain a valid partial token and verification data, and cause a victim's browser to resume that attacker-controlled flow. This could authenticate the victim's browser as the attacker's account. The issue affects applications using partial pipeline steps such as mailvalidation or custom steps decorated with @partial. The issue has been fixed in version 5.0.0 by binding partial pipeline resumes to the originating browser session.
— 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
social-auth-coreto a version that resolves this vulnerability.Fixed in 5.0.0 - Configuration
Disable resumable partial pipeline steps, including mail_validation and custom steps decorated with @partial.
Python Social Auth resumable partial pipeline steps = disabled - Compensating control
Until a patched version can be deployed, avoid accepting partial resume links from untrusted contexts when those flows are required.
Event History
Frequently Asked Questions
Which applications are affected by this issue?
Applications using social-auth-core versions prior to 5.0.0 are affected if they use resumable partial pipeline steps, including mail_validation or custom steps decorated with @partial. Applications that do not use partial pipeline resumes are not identified as affected by the available information.
What must an attacker do to exploit it?
The attacker must start an authentication flow and obtain a valid partial token and its verification data. They must then cause a victim to resume that attacker-controlled flow in the victim's browser, which requires user interaction.
What is the practical impact?
A successful attack can authenticate the victim's browser as the attacker's account. The supplied severity vector indicates low confidentiality and integrity impact, with no availability impact.
What should be done if an application uses partial pipeline steps?
Upgrade social-auth-core to version 5.0.0, which binds partial-pipeline resumes to the browser session that originated them. The provided information does not specify an alternative mitigation for installations that cannot upgrade.