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).
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | qtwebsockets-opensource-src | 5.15.1-2 | — |
| Debian 13 | qtwebsockets-opensource-src | 5.15.1-2 | — |
| Debian 12 | qtwebsockets-opensource-src | 5.15.1-2 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | qtwebsockets-opensource-src | No fix yet | — |
| Ubuntu 18.04 LTS | qtwebsockets-opensource-src | No fix yet | — |
| Ubuntu 16.04 LTS | qtwebsockets-opensource-src | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | qt5-qtbase +9 | 5.12.5-6.el8 | RHSA-2020:4690 |
| RHEL 8 | qt5-qttools +15 | 5.12.5-2.el8 | RHSA-2020:4690 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | qt5-qtbase-static | 5.12.5-6.el8 | ALSA-2020:4690 |
| AlmaLinux 8 | qt5-qttools-static | 5.12.5-2.el8 | ALSA-2020:4690 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | qt5-qtwebsockets | 5.12.5-2.el8 | RLSA-2020:4690 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 2 (CBL-Mariner) | qt5-qtsvg | 5.12.11-3 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | qt5-qtbase +9 | 5.12.5-6.el8 | ELSA-2020-4690 |
| Oracle Linux 8 | qt5-qttools +15 | 5.12.5-2.el8 | ELSA-2020-4690 |
Advisories 4
- ALSA-2020:4690 Moderate: qt5-qtbase and qt5-qtwebsockets security and bug fix update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2020:4690 Red Hat Security Advisory: qt5-qtbase and qt5-qtwebsockets security and bug fix update Red Hat Security Advisories (RHSA) · Oct 9, 2026
- RLSA-2020:4690 Moderate: qt5-qtbase and qt5-qtwebsockets security and bug fix update Rocky Linux Security Advisories · Feb 5, 2026
- ELSA-2020-4690 Moderate: qt5-qtbase and qt5-qtwebsockets security and bug fix update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 10, 2020