What’s Vulnerable › Vulnerabilities

CVE-2018-21035

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-02-28 · updated 2026-06-17
• Weakness: CWE-770

Description

In Qt through 5.14.1, the WebSocket implementation accepts up to 2GB for frames and 2GB for messages. Smaller limits cannot be configured. This makes it easier for attackers to cause a denial of service (memory consumption).

Affected products

• Qt: through 5.14.1

References

• https://bugreports.qt.io/browse/QTBUG-70693
• https://codereview.qt-project.org/c/qt/qtwebsockets/+/284735
• https://bugreports.qt.io/browse/QTBUG-70693
• https://codereview.qt-project.org/c/qt/qtwebsockets/+/284735

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