Symfony before 2.8.6 and 3.x before 3.0.6 allows remote attackers to bypass authentication by logging in with an empty password and valid username, which triggers an unauthenticated bind.

References

• https://nvd.nist.gov/vuln/detail/CVE-2016-2403
• https://www.debian.org/security/2018/dsa-4262
• http://symfony.com/blog/cve-2016-2403-unauthorized-access-on-a-misconfigured-ldap-server-when-using-an-empty-password
• https://web.archive.org/web/20210123224944/http://www.securityfocus.com/bid/96137
• https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security-core/CVE-2016-2403.yaml
• https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security/CVE-2016-2403.yaml
• https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2016-2403.yaml
• https://symfony.com/cve-2016-2403