CVE-2025-5991: Qt

Low severity, CVSS 2.1. EPSS: 0.1% chance of exploitation in the next 30 days.

There is a "Use After Free" vulnerability in Qt's QHttp2ProtocolHandler in the QtNetwork module. This only affects HTTP/2 handling, HTTP handling is not affected by this at all. This happens due to a race condition between how QHttp2Stream uploads the body of a POST request and the simultaneous handling of HTTP error responses. This issue only affects Qt 6.9.0 and has been fixed for Qt 6.9.1.

Affected products

• Qt Qt: version 6.9.0 only

Published 2025-06-11. Last modified 2026-07-29.