Microsoft Windows: privilege escalation flaw under attack

What is affected

Microsoft Windows is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.

Microsoft Windows Agere Modem Driver contains an untrusted pointer dereference vulnerability that allows for privilege escalation. An attacker who successfully exploited this vulnerability could gain administrator privileges.

What an attacker can do

This is a privilege escalation flaw. It lets an attacker turn limited access into full administrator control. Attackers pair it with another flaw or a malicious file: once anything of theirs runs on the device, this bug lets it take over completely.

How it is reached

Needs access to the device or a file opened on it

Access the attacker needs

A basic user account

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. Update Microsoft Windows now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
2. Turn on automatic updates so the next fix arrives without you having to look for it.
3. If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• msrc.microsoft.commsrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2025-24990

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on October 14, 2025, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by November 4, 2025, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 6.4% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 93% of all scored vulnerabilities.

Its CVSS severity score is 7.8 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

Microsoft is aware of vulnerabilities in the third party Agere Modem driver that ships natively with supported Windows operating systems. This is an announcement of the upcoming removal of ltmdm64.sys driver. The driver has been removed in the October cumulative update. Fax modem hardware dependent on this specific driver will no longer work on Windows. Microsoft recommends removing any existing dependencies on this hardware.