CVE-2025-61783 is a vulnerability classified under CWE-303 (Incorrect Implementation of Authentication Algorithm) affecting the python-social-auth library's social-app-django component in versions prior to 5.6.0. The issue arises because the authentication pipeline incorrectly associates users by e-mail addresses even when the associate_by_email pipeline step is not included. This behavior can be exploited when a third-party authentication service used for social login does not properly validate or enforce uniqueness of e-mail addresses, allowing an attacker to impersonate or link to another user's account by providing a matching e-mail. The vulnerability does not require user interaction, privileges, or authentication to exploit, but the attack complexity is high because it depends on the external authentication provider's policies and implementation. The impact includes potential unauthorized access to user accounts, compromising confidentiality and integrity of user data. The vulnerability has a CVSS 4.0 base score of 6.3 (medium severity), reflecting network attack vector, high attack complexity, no privileges or user interaction required, and limited confidentiality and integrity impact. The issue was patched in version 5.6.0 of social-app-django. No known exploits are reported in the wild as of the publication date. Organizations relying on social authentication with python-social-auth should upgrade promptly and verify their third-party authentication providers enforce strict e-mail validation and uniqueness to mitigate risk.

For European organizations, this vulnerability poses a risk of unauthorized account access through social authentication mechanisms, potentially leading to data breaches, unauthorized transactions, or privilege escalation within affected applications. Organizations in sectors such as finance, healthcare, government, and e-commerce that rely on python-social-auth for user authentication are particularly vulnerable. The compromise of user accounts can lead to violations of GDPR due to unauthorized access to personal data, resulting in regulatory penalties and reputational damage. Additionally, attackers could leverage compromised accounts to conduct further attacks or fraud. The dependency on third-party authentication providers' e-mail validation policies means that organizations using providers with lax e-mail verification are at higher risk. The medium severity rating indicates a moderate but non-trivial threat that requires timely remediation to prevent exploitation. The lack of known exploits in the wild suggests an opportunity for proactive defense before widespread attacks occur.

1. Upgrade all instances of python-social-auth social-app-django to version 5.6.0 or later to apply the official patch addressing this vulnerability. 2. Audit and review the authentication pipeline configuration to ensure the associate_by_email step is explicitly controlled and not implicitly enabled. 3. Evaluate and enforce strict e-mail validation and uniqueness policies with all third-party social authentication providers used, ensuring they verify e-mail ownership and prevent duplicate e-mail registrations. 4. Implement additional application-level checks to verify user identity beyond e-mail association, such as multi-factor authentication or secondary verification steps. 5. Monitor authentication logs for unusual account linking or login patterns that could indicate exploitation attempts. 6. Educate development and security teams about the risks of implicit authentication behaviors and the importance of secure pipeline configurations. 7. Consider isolating or restricting social authentication features in sensitive applications until the patch and mitigations are fully deployed. 8. Engage with third-party providers to confirm their compliance with secure e-mail validation standards and request improvements if necessary.