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Unauthorized Password Reset in Microsoft Defender for IoT
CVE-2021-42310 is a critical vulnerability in Microsoft Defender for IoT affecting the product’s ZIP-based password recovery workflow in both cloud-connected and on-premises deployments. The recovery mechanism accepts an uploaded archive containing a signing certificate, issuer certificate, and a password reset manifest. The implementation performs validation across separate Python and Java components, introducing a time-of-check/time-of-use flaw in the recovery flow. In addition, the Java-side validation logic does not properly verify the trustworthiness of the supplied signing certificate and only checks whether the reset manifest is signed by the attached certificate, allowing use of attacker-generated self-signed material. The recovery logic also uses insufficient subscription validation, enabling bypass of authorization checks. Together, these flaws allow an unauthenticated attacker to submit a crafted recovery package and reset the password of a privileged account without authorization.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation allows unauthorized reset of the privileged Defender for IoT user account. Because the same credentials are used for the web interface and the SSH service on affected systems, compromise of this account can provide broad administrative access to the appliance. This can enable full takeover of the Defender for IoT instance and create a path to further compromise of monitored environments.
If you can’t patch tonight, do this now.
If immediate patching is not possible, restrict access to the password recovery interface to trusted administrative networks only, minimize exposure of management interfaces, and closely monitor for anomalous password reset activity and privileged logins. As a precaution, rotate privileged credentials and limit SSH and management-plane access until updates can be applied. Log review for irregular administrative actions is advisable.
Patch, then assume compromise.
Apply Microsoft’s security updates released for Microsoft Defender for IoT that address CVE-2021-42310 and the associated password recovery validation flaws. After patching, rotate or revoke privileged credentials that were present on the platform prior to remediation, as those credentials may have been exposed or reset by an attacker. Review authentication and administrative access logs for signs of unauthorized password recovery or account misuse.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
2 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.