CVE-2025-5991 Use after free in QHttp2ProtocolHandler
A race condition in Qt's HTTP/2 handler allows attackers to trigger a use-after-free, potentially leading to code execution or crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-5991?
CVE-2025-5991 is a low-severity use after free vulnerability in Qt, published on 11 Jun 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-416
Which versions are affected by CVE-2025-5991?
How do I fix CVE-2025-5991?
Upgrade to a fixed version.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-5991 being exploited?
There is no known exploitation of CVE-2025-5991 in the wild and no public exploit code.
Sources
Also known as ECHO-e7f4-9860-3083, GHSA-xv5c-vg59-hj7x, UBUNTU-CVE-2025-5991.