CVE-2026-4208 in E-Mail MFA Provider Extension
Summary
by MITRE • 03/17/2026
The extension fails to properly reset the generated MFA code after successful authentication. This leads to a possible MFA bypass for future login attempts by providing an empty string as MFA code to the extensions MFA provider.
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Analysis
by VulDB Data Team • 03/22/2026
The vulnerability described in CVE-2026-4208 represents a critical flaw in multi-factor authentication implementation within a software extension. This weakness stems from inadequate state management during the authentication process, specifically concerning the handling of time-based one-time passwords or similar MFA mechanisms. The flaw allows an attacker to potentially bypass the second factor of authentication by exploiting the improper reset behavior of generated codes, creating a persistent security weakness that could be exploited across multiple login attempts. The root cause lies in the extension's failure to properly invalidate or reset the MFA code state after successful authentication, leaving the system in a vulnerable state where subsequent authentication attempts can be satisfied with an empty string value.
From a technical perspective, this vulnerability aligns with CWE-284, which addresses improper access control, and CWE-305, which deals with authentication bypass through use of cached authentication data. The flaw manifests as a state management error where the system does not properly transition from an authenticated state back to an unauthenticated state for MFA validation. When a legitimate user successfully authenticates, the extension should invalidate the previously generated MFA code and reset the authentication context to ensure that any subsequent login attempt requires fresh MFA verification. However, the current implementation fails to execute this reset mechanism properly, allowing the same MFA code or empty string input to be accepted for future authentication attempts, effectively creating a backdoor that bypasses the intended security controls.
The operational impact of this vulnerability extends beyond simple authentication bypass, potentially enabling credential stuffing attacks, session hijacking, and unauthorized access to protected systems or data. Attackers can exploit this weakness by first authenticating successfully with valid credentials, then leveraging the improper code reset to gain access to additional accounts or systems without proper MFA verification. This vulnerability particularly affects environments where the extension is used for critical access control, such as enterprise applications, cloud services, or systems managing sensitive data. The risk is amplified when the extension is part of a larger authentication ecosystem where MFA is a required security control, as it undermines the fundamental security principle that each authentication attempt should require independent verification of the second factor.
The mitigation strategy for CVE-2026-4208 requires immediate implementation of proper state management protocols within the extension's authentication logic. Security teams should ensure that after successful authentication, the MFA code generation context is completely reset and that any cached or stored MFA values are invalidated. This includes implementing proper session management, ensuring that MFA tokens are only valid for a single authentication attempt, and enforcing strict validation of MFA inputs. Organizations should also consider implementing monitoring and alerting mechanisms to detect unusual authentication patterns that might indicate exploitation of this vulnerability. From an ATT&CK framework perspective, this vulnerability maps to technique T1566.002 for credential access through phishing with malicious MFA codes and T1078.004 for legitimate credentials, as it allows attackers to bypass MFA protections that would normally prevent unauthorized access. The fix should involve comprehensive code review and testing of authentication flows, ensuring that all authentication states are properly managed and that the system enforces proper MFA validation for each individual login attempt rather than allowing cached or stale MFA values to be reused.