CVE-2025-5455 Possible denial of service when passing malformed data in a URL to qDecodeDataUrl

High 8.4 Published 2 Jun 2025 Updated 29 Jul 2026

Attackers can cause a denial of service by passing malformed URLs to Qt's qDecodeDataUrl function when assertions are enabled.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2025-5455?

CVE-2025-5455 is a high-severity denial of service vulnerability in Qt, published on 2 Jun 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

An issue was found in the private API function qDecodeDataUrl() in QtCore, which is used in QTextDocument and QNetworkReply, and, potentially, in user code.

If the function was called with malformed data, for example, an URL that contained a "charset" parameter that lacked a value (such as "data:charset,"), and Qt was built with assertions enabled, then it would hit an assertion, resulting in a denial of service (abort).

This impacts Qt up to 5.15.18, 6.0.0->6.5.8, 6.6.0->6.8.3 and 6.9.0. This has been fixed in 5.15.19, 6.5.9, 6.8.4 and 6.9.1.

Weakness: CWE-20

Which versions are affected by CVE-2025-5455?

Linux distribution packages (40)

`qt6-qtbase-common` AlmaLinux:10	All versions	`6.8.1-9.el10_0`
`qt5-qtbase` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt5-qtbase-common` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt5-qtbase-devel` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt5-qtbase-examples` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt5-qtbase-gui` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt5-qtbase-mysql` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt5-qtbase-odbc` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt5-qtbase-postgresql` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt5-qtbase-private-devel` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt5-qtbase-static` AlmaLinux:9	All versions	`5.15.9-11.el9_6`
`qt6-qtbase` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-common` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-debuginfo` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-debugsource` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-devel` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-devel-debuginfo` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-examples` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-examples-debuginfo` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-gui` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-gui-debuginfo` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-mysql` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-mysql-debuginfo` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-odbc` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-odbc-debuginfo` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-postgresql` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-postgresql-debuginfo` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-private-devel` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-static` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt6-qtbase-tests-debuginfo` Red Hat:enterprise_linux:10.0	All versions	`0:6.8.1-9.el10_0`
`qt5-qtbase` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`
`qt5-qtbase-common` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`
`qt5-qtbase-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`
`qt5-qtbase-debugsource` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`
`qt5-qtbase-devel` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`
`qt5-qtbase-devel-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`
`qt5-qtbase-examples` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`
`qt5-qtbase-examples-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`
`qt5-qtbase-gui` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`
`qt5-qtbase-gui-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:5.15.9-11.el9_6`

How do I fix CVE-2025-5455?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-5455 being exploited?

There is no known exploitation of CVE-2025-5455 in the wild and no public exploit code.

Sources

Also known as ALSA-2025:9462, ALSA-2025:9486, AZL-64349, AZL-64361, DEBIAN-CVE-2025-5455, ECHO-a29a-8133-4b8d and 14 more.