In Qt through 5.14.1, the WebSocket implementation accepts up to 2GB for frames and 2GB…
Priority LOW 37CWE-770Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 2 fixed, 1 without a fix
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-770.
Summary
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).
Why it matters now
EPSS 0.02339 83rd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial Red Hat: 1 advisoryRed Hat: 2 fixed, 1 without a fix
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
Remediation
Red Hat 1 advisory
- RHSA-2020:4690 Released 2020-11-04 · Red Hat rating Moderateqt5-qtbase and qt5-qtwebsockets security and bug fix update
- Red Hat CodeReady Linux Builder (v. 8) qt5-qtbase-static-5.12.5-6.el8, qt5-qttools-static-5.12.5-2.el8
- Red Hat Enterprise Linux AppStream (v. 8) qt5-assistant-5.12.5-2.el8, qt5-designer-5.12.5-2.el8, qt5-doctools-5.12.5-2.el8 +21
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Will not fix |
| Red Hat CodeReady Linux Builder (v. 8) | Fixed | RHSA-2020:4690 |
| Red Hat Enterprise Linux AppStream (v. 8) | Fixed | RHSA-2020:4690 |
Timeline
- 2026-10-02 Threatist record created from CVE-2018-21035
- 2026-10-03 Alias added: GHSA-xhq4-5269-2ffv
References
More Qt vulnerabilities
- TI-2024-23902 QAbstractOAuth in Qt Network Authorization in Qt before 5.15.17, 6.x before 6.2.13, 6.3.x… CVSS 3.1CRITICAL 9.8
- TI-2022-21359 Heap-based buffer overflow in Qt CVSS 3.1HIGH 8.8
- TI-2022-19524 Integer overflow in Qt CVSS 3.1HIGH 8.8
- TI-2023-18997 In Qt before 5.15.15, 6.x before 6.2.9, and 6.3.x through 6.5.x before 6.5.2, there can… CVSS 3.1HIGH 7.5
- TI-2021-09305 Integer Overflow vulnerability in qsvghandler.cpp in Qt qtsvg versions 5.15.1, 6.0.0… CVSS 3.1MEDIUM 5.5
- TI-2023-28356 An issue was discovered in the HTTP2 implementation in Qt before 5.15.17, 6.x before… CVSS 3.1CRITICAL 9.8
Sources
- CVE-2018-21035 · CVE Program
- CVE-2018-21035 · NVD
- FIRST EPSS
- GHSA-xhq4-5269-2ffv · GitHub Advisory Database · CC BY 4.0
- CVE-2018-21035 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences