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Microsoft Defender for Endpoint is presently facing a glitch that produces erroneous alerts regarding outdated Basic Input/Output System (BIOS) versions, particularly impacting Dell devices.
This concern, monitored by Microsoft under the reference ID DZ1163521, is leading security teams to receive alerts prompting firmware updates for devices that are already up to date.
This situation has resulted in confusion and unnecessary administrative burden for organizations that depend on the endpoint security platform for managing vulnerabilities. Microsoft has acknowledged the matter and is actively working towards a solution.
The glitch particularly affects organizations utilizing Microsoft Defender for Endpoint to oversee their Dell hardware devices. Users and security administrators experiencing this issue are receiving repeated notifications indicating that a device’s BIOS is susceptible and requires an update.
However, investigations reveal that the BIOS version on the flagged device is indeed the latest version provided by Dell.
Surge of Erroneous BIOS Alerts
This surge of misleading alerts presents considerable operational hurdles, including alert fatigue among security analysts, who may become desensitized to real threats.
Moreover, it utilizes valuable time and resources, as IT teams are compelled to investigate and confirm these non-issues, diverting their focus from actual security incidents.
Microsoft has examined the situation and identified the core issue as a code bug within the Defender for Endpoint service. According to their update, the defect lies within the specific logic responsible for retrieving and assessing vulnerability data related to Dell devices.
This flawed code incorrectly interprets the BIOS version information from the endpoints, causing it to misidentify current systems as vulnerable.
The situation underscores the challenges involved in accurately managing vendor-specific firmware and software versions across a varied range of hardware within a centralized security monitoring solution.
The issue does not reflect a vulnerability within the Dell BIOS itself but indicates a processing error inside Microsoft’s security platform.
In a communication update issued on October 2, 2025, Microsoft confirmed that its engineering team has effectively created a fix to resolve the code bug.
While the problem’s status remains “OPEN,” the organization is now prepping to deploy the corrective patch to the affected environment. Microsoft has stated that it anticipates deployment to begin around the time of its next scheduled update.
Organizations affected by this situation are encouraged to keep an eye on the Microsoft service health dashboard for advisory DZ1163521 for the most current details on the fix rollout.
Until the patch is entirely deployed, administrators will need to manually confirm the BIOS status of identified Dell devices to differentiate these false alarms from legitimate threats.
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