How severe is CVE-2025-5991?

CVE-2025-5991 has a CVSS 4.0 base score of 2.1, rated low severity.

Is CVE-2025-5991 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2025-5991?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-5991 have an EU (EUVD) identifier?

Yes. CVE-2025-5991 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-18092.

When was CVE-2025-5991 published?

CVE-2025-5991 was published on 2025-06-11 and last updated on 2026-06-17.

CVE-2025-5991

CVE-2025-5991 is a low-severity vulnerability with a CVSS 4.0 base score of 2.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-416.

Key facts

Severity: Low (CVSS 4.0 base score 2.1)
EPSS exploit prediction: 0% (2nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-18092
Weakness: CWE-416
Published: 2025-06-11
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2025-5991?: 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.
How severe is CVE-2025-5991?: CVE-2025-5991 has a CVSS 4.0 base score of 2.1, rated low severity.
Is CVE-2025-5991 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2025-5991?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-5991 have an EU (EUVD) identifier?: Yes. CVE-2025-5991 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-18092.
When was CVE-2025-5991 published?: CVE-2025-5991 was published on 2025-06-11 and last updated on 2026-06-17.

References

https://codereview.qt-project.org/c/qt/qtbase/+/643777

Other CWE-416 (Use After Free) vulnerabilities

CVE-2026-13782 — Critical (CVSS 10.0): Use after free in Browser in Google Chrome prior to 150.0.7871.47 allowed a remote attacker who had compromised the…
CVE-2026-4725 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149…
CVE-2026-4688 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox…
CVE-2025-24085 — Critical (CVSS 10.0): A use after free issue was addressed with improved memory management. This issue is fixed in iOS 18.3 and iPadOS 18.3,…
CVE-2024-43102 — Critical (CVSS 10.0): Concurrent removals of certain anonymous shared memory mappings by using the UMTX_SHM_DESTROY sub-request of…
CVE-2021-32495 — Critical (CVSS 10.0): Radare2 has a use-after-free vulnerability in pyc parser's get_none_object function. Attacker can read freed memory…

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