CVE-2025-6338: Qt

Critical severity, CVSS 9.2. EPSS: 0.4% chance of exploitation in the next 30 days.

There is an incomplete cleanup vulnerability in Qt Network's Schannel support on Windows which can lead to a Denial of Service over a long period. This issue affects Qt from 5.15.0 through 6.8.3, from 6.9.0 before 6.9.2.

Affected products

• Qt Qt: from 5.15.0, up to and including 6.8.3; from 6.9.0, before 6.9.2 (fixed in 6.9.2)

Published 2025-10-16. Last modified 2026-10-09.