CVE-2021-23017

Publication date 25 May 2021

Last updated 25 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
nginx	22.04 LTS jammy	Fixed 1.18.0-6ubuntu9
	21.10 impish	Fixed 1.18.0-6ubuntu9
	21.04 hirsute	Fixed 1.18.0-6ubuntu8.2
	20.10 groovy	Fixed 1.18.0-6ubuntu2.2
	20.04 LTS focal	Fixed 1.18.0-0ubuntu1.2
	18.04 LTS bionic	Fixed 1.14.0-0ubuntu1.9
	16.04 LTS xenial	Fixed 1.10.3-0ubuntu0.16.04.5+esm1
	14.04 LTS trusty	Fixed 1.4.6-1ubuntu3.9+esm2

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Patch details

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

Package	Patch details
nginx	Upstream: http://nginx.org/download/patch.2021.resolver.txt

Severity score breakdown

Parameter	Value
Base score	7.7 · High
Attack vector	Network
Attack complexity	High
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	High
Integrity impact	High
Availability impact	Low
Vector	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L