dbcve.org
Improper Input ValidationWeakness · CWE-20

CVE-2025-5455

HIGH · 8.4 CVSS v4.0 Published 2025-06-02
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
91/100
Remediation priority · Urgent
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A malformed data URL with an empty charset parameter (e.g., 'data:charset,') triggers an assertion failure in QtCore's private qDecodeDataUrl() function, causing denial of service via process abort. This function is used by QTextDocument, QNetworkReply, and potentially custom code.

MitigationUpdate Qt to version 5.15.19, 6.5.9, 6.8.4, or 6.9.1 and later, or ensure production builds disable assertions to prevent the abort condition.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
Authentication
X
User interaction
A
Scope
X

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:H/SC:N/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:U/V:X/RE:M/U:Clear

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the Qt version in your environment
    Run 'qmake --version' or check the Qt libraries linked in your application using 'ldd <executable>' | grep -i qt. If you have source code, check the qglobal.h file for QT_VERSION or QT_VERSION_STR macros.
    Affected if The installed Qt version is earlier than 5.15.19, 6.5.9, 6.8.4, or 6.9.1
  2. Determine if your application uses QTextDocument or QTextEdit
    Search your source code for '#include <QTextDocument>' or '#include <QTextEdit>' and verify these classes are used to render or process content that could contain data URLs.
    Affected if Your application uses QTextDocument or QTextEdit to render HTML or other content that might contain data URLs
  3. Determine if your application uses QNetworkReply
    Search your source code for '#include <QNetworkReply>' or '#include <QNetworkAccessManager>' and verify your application makes network requests or processes remote content.
    Affected if Your application uses QNetworkReply or QNetworkAccessManager to fetch or process network content that might include data URLs
  4. Check for custom code using qDecodeDataUrl
    Search your source code for calls to 'qDecodeDataUrl' or similar data URL parsing functions, and review any third-party libraries that may integrate with Qt's data URL handling.
    Affected if Your application or its dependencies directly call qDecodeDataUrl or implement custom data URL parsing
  5. Verify if Qt assertions are enabled in your build
    Check your build configuration for QT_NO_DEBUG or Q_ASSERT disabled. Look for 'DEFINES += QT_NO_DEBUG' in your .pro file, or inspect if the Qt library was built with assertions disabled (assertions are typically enabled in debug builds and disabled in release builds).
    Affected if Your application runs with Qt assertions enabled (typically debug builds) and processes untrusted content containing malformed data URLs

Your environment is affected if you run a Qt version earlier than 5.15.19/6.5.9/6.8.4/6.9.1 AND your application uses QTextDocument, QNetworkReply, or custom code that parses data URLs from untrusted sources while running with assertions enabled.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update Qt to version 5.15.19, 6.5.9, 6.8.4, or 6.9.1 and later, or ensure production builds disable assertions to prevent the abort condition.

Recommended fix High confidence

Qt 5.15.19 for 5.15.x users; Qt 6.5.9 for 6.5.x users; Qt 6.8.4 for 6.6.x-6.8.x users; Qt 6.9.1 for 6.9.x users

  1. 1. Identify the current Qt version in use by checking your project dependencies or Qt installation
  2. 2. Determine which Qt major version branch you are using (Qt 5.15.x, 6.5.x, 6.6.x-6.8.x, or 6.9.x)
  3. 3. Upgrade Qt to the corresponding fixed version: Qt 5.15.18 → 5.15.19, Qt 6.5.8 → 6.5.9, Qt 6.6.x-6.8.3 → 6.8.4, or Qt 6.9.0 → 6.9.1
  4. 4. For package managers: update via your distribution's package manager or download the new version from qt.io
  5. 5. For dependency management: update the Qt version specification in your build configuration (e.g., qmake, CMake, qbs)
  6. 6. Rebuild and test your application to ensure the upgrade does not introduce regressions
Caveat Minor version upgrades within stable branches typically have minimal breaking changes, but review the Qt release notes for your target version to check for any API or behavior changes that may affect your application

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-5455 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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