# 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.

- **Severity:** Low 2.1 (`CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Jun 2025
- **Updated:** 29 Jul 2026
- **Also known as:** ECHO-e7f4-9860-3083, GHSA-xv5c-vg59-hj7x, UBUNTU-CVE-2025-5991

## 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 (Use After Free)

## Which versions are affected by CVE-2025-5991?


## How do I fix CVE-2025-5991?

Upgrade to a fixed version.

## Is CVE-2025-5991 being exploited?

There is no known exploitation of CVE-2025-5991 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-5991 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2025-5991 in the wild and no public exploit code.

Affected product: Qt. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-5991/ (Markdown: https://insights.sbomify.com/CVE-2025-5991/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-5991
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-5991
- OSV: https://osv.dev/vulnerability/CVE-2025-5991

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-5991/
Summaries are generated and may contain mistakes; the official description above is the record.