CVE-2020-26136 in SilverStripe
Summary
by MITRE • 06/09/2021
In SilverStripe through 4.6.0-rc1, GraphQL doesn't honour MFA (multi-factor authentication) when using basic authentication.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 06/11/2021
The vulnerability described in CVE-2020-26136 represents a critical security flaw in the SilverStripe content management system that affects versions through 4.6.0-rc1. This issue specifically impacts the GraphQL API implementation within SilverStripe, creating a significant bypass opportunity for unauthorized access attempts. The flaw manifests when basic authentication is employed, allowing attackers to potentially circumvent multi-factor authentication requirements that should normally be enforced for GraphQL endpoints. This represents a fundamental breakdown in the authentication flow where the system fails to properly validate that additional authentication factors have been successfully completed before granting access to protected GraphQL resources.
The technical implementation of this vulnerability stems from how SilverStripe's GraphQL layer handles authentication contexts when basic authentication credentials are presented. In a properly configured system, multi-factor authentication should be enforced regardless of the authentication method used, ensuring that even if an attacker obtains valid basic authentication credentials, they cannot bypass the additional security layers required for sensitive operations. The flaw occurs because the GraphQL interface does not properly verify or enforce the MFA status of authenticated users, effectively treating basic authentication as if it were equivalent to full authentication status without proper factor validation.
From an operational impact perspective, this vulnerability creates a serious risk for organizations using SilverStripe with GraphQL APIs, particularly those handling sensitive data or requiring strict access controls. Attackers could potentially exploit this weakness to gain unauthorized access to GraphQL endpoints that should require additional authentication factors, leading to data breaches, unauthorized modifications, or privilege escalation. The risk is compounded because basic authentication credentials are often easier to obtain through various attack vectors such as credential stuffing, brute force attempts, or compromised accounts, making this bypass particularly dangerous in environments where MFA is implemented as a security control.
Organizations should immediately implement mitigations including upgrading to SilverStripe versions that address this vulnerability, implementing additional access controls for GraphQL endpoints, and ensuring proper authentication auditing is in place. The vulnerability aligns with CWE-305 authentication bypass issues and could potentially map to ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting. Security teams should also consider implementing network-level controls such as rate limiting and IP whitelisting for GraphQL endpoints, while ensuring that all authentication flows properly validate MFA status regardless of authentication method used. Regular security assessments should verify that authentication mechanisms are properly enforced across all API endpoints, including GraphQL interfaces, to prevent similar bypass scenarios from occurring in other system components.