CVE-2026-53904: Account Denial of Service in MCO
MCO is vulnerable to Account Denial of Service due to improper implementation of password reset functionality. Each password reset request invalidates previously set password as well as previously issued temporary passwords, furthermore, password resets are not limited in any way. An attacker who provides victim's email and answer to their security question, can successfully initiate the reset process and continuously invalidate credentials, effectively locking the victim out of their account. Answering security questions has a limited number of tries which lowers the risk of this vulnerability.
Because vendor contact attempts were unsuccessful, the vulnerability has only been confirmed in version 25.3.3.1 but may also affect other versions.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
Rely on the existing limit on security-question attempts (limited number of tries) to reduce exposure to the Account Denial of Service scenario described for MCO password reset abuse.
- Compensating control
Apply an external rate limit/control on password reset requests for affected users/accounts to prevent unlimited password reset initiation, since password resets are described as not limited in any way.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-53904?
CVE-2026-53904 has a medium severity rating of 6.3 on the CVSS scale.
What type of vulnerability is CVE-2026-53904?
CVE-2026-53904 is classified as an Account Denial of Service vulnerability due to improper password reset implementation.
How do I fix CVE-2026-53904?
To fix CVE-2026-53904, ensure that the password reset functionality limits the number of requests and properly manages previously set passwords.
What software is affected by CVE-2026-53904?
CVE-2026-53904 affects the MCO software.
What are the potential impacts of CVE-2026-53904?
An attacker exploiting CVE-2026-53904 can cause legitimate users to be locked out of their accounts through excessive password reset requests.