CVE-2021-33193

Publication date 16 August 2021

Last updated 25 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
apache2	22.04 LTS jammy	Fixed 2.4.48-3.1ubuntu2
	21.10 impish	Fixed 2.4.48-3.1ubuntu2
	21.04 hirsute	Fixed 2.4.46-4ubuntu1.2
	20.04 LTS focal	Fixed 2.4.41-4ubuntu3.5
	18.04 LTS bionic	Fixed 2.4.29-1ubuntu4.17
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not affected

Notes

mdeslaur

commits for trunk and 2.4 don't match, needs investigation commit for 2.4 is the one listed in the vulnerability report as of 2021-08-26, no new version of apache contains the fix

Patch details

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

Package	Patch details
apache2	Upstream: f990e5e Upstream: ecebcc0

Severity score breakdown

Parameter	Value
Base score	7.5 · High
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	None
Integrity impact	High
Availability impact	None
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References

Related Ubuntu Security Notices (USN)

USN-5090-1
Apache HTTP Server vulnerabilities
27 September 2021