CVE-2018-21035

Publication date 28 February 2020

Last updated 26 August 2025

Ubuntu priority

Cvss 3 Severity Score

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).

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
qtwebsockets-opensource-src	25.10 questing	Not affected
	25.04 plucky	Not affected
	24.10 oracular	Not affected
	24.04 LTS noble	Not affected
	23.10 mantic	Not affected
	23.04 lunar	Not affected
	22.10 kinetic	Not affected
	22.04 LTS jammy	Not affected
	21.10 impish	Not affected
	21.04 hirsute	Not affected
	20.10 groovy	Ignored end of life
	20.04 LTS focal	Needs evaluation
	19.10 eoan	Ignored end of life
	18.04 LTS bionic	Needs evaluation
	16.04 LTS xenial	Needs evaluation
	14.04 LTS trusty	Not in release

Notes

mdeslaur

upstream commit just adds new settings allowing users to lower allowed frame/message size, it doesn't change the default behaviour

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
qtwebsockets-opensource-src	Upstream: ed93680

Severity score breakdown

Parameter	Value
Base score	8.6 · High
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Changed
Confidentiality	None
Integrity impact	None
Availability impact	High
Vector	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H