CVE-2026-4208

High

Published: 17 March 2026

Published

17 March 2026

Modified

25 April 2026

KEV Added

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Patch

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CVSS Score 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0007 21.6th percentile

Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-4208 is a high-severity Authorization Bypass Through User-Controlled Key (CWE-639) vulnerability in Mrsilaz Mfa Mail. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 21.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 IA-5 (Authenticator Management) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 2 other techniques. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

IA-5 Authenticator Management good match

prevent

IA-5 mandates proper management, refresh, and invalidation of authenticators like MFA codes after successful authentication, directly preventing reuse or bypass via unreset states and empty strings.

SI-10 Information Input Validation partial match

prevent

SI-10 requires validation of inputs such as MFA codes, rejecting empty or invalid values to block bypass attempts exploiting improper code handling.

SI-2 Flaw Remediation good match

prevent

SI-2 ensures timely identification, reporting, and patching of flaws like this MFA reset failure, preventing exploitation of the vulnerability.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1556.006 Multi-Factor Authentication Defense Impairment

Adversaries may disable or modify multi-factor authentication (MFA) mechanisms to enable persistent access to compromised accounts.

attack.mitre.org →

T1078 Valid Accounts Stealth

Adversaries may obtain and abuse credentials of existing accounts as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion.

attack.mitre.org →

Why these techniques?

Vuln in public-facing TYPO3 CMS extension directly enables remote MFA bypass via empty code submission after failed reset (CWE-639 authz flaw), facilitating T1190 exploitation, T1556.006 MFA modification/bypass for access, and T1078 abuse of valid accounts.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

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.

Deeper analysisAI

CVE-2026-4208 is a vulnerability in a TYPO3 extension that fails to properly reset the generated MFA code after successful authentication. This flaw enables a possible MFA bypass for future login attempts by submitting an empty string as the MFA code to the extension's MFA provider. The issue carries a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) and maps to CWE-639 (Authorization Bypass Through User-Controlled Key). It was published on 2026-03-17.

The vulnerability can be exploited remotely by an attacker with low privileges, such as an authenticated user requiring minimal privileges (PR:L), with low attack complexity and no user interaction. By leveraging the failure to reset the MFA code post-authentication, the attacker submits an empty string during subsequent login attempts to bypass MFA validation, potentially resulting in high impacts to confidentiality, integrity, and availability.

Mitigation details are provided in the TYPO3 security advisory at https://typo3.org/security/advisory/typo3-ext-sa-2026-007.