CVE-2021-3618

Publication date 23 March 2022

Last updated 18 August 2025

Ubuntu priority

Low

Why this priority?

Cvss 3 Severity Score

7.4 · High

Score breakdown

Description

ALPACA is an application layer protocol content confusion attack, exploiting TLS servers implementing different protocols but using compatible certificates, such as multi-domain or wildcard certificates. A MiTM attacker having access to victim's traffic at the TCP/IP layer can redirect traffic from one subdomain to another, resulting in a valid TLS session. This breaks the authentication of TLS and cross-protocol attacks may be possible where the behavior of one protocol service may compromise the other at the application layer.

Read the notes from the security team

Status

Package Ubuntu Release Status
nginx 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 Ignored end of life, was needed
22.04 LTS jammy
Fixed 1.18.0-6ubuntu14.1
21.10 impish
Fixed 1.18.0-6ubuntu11.1
21.04 hirsute Ignored end of life
20.04 LTS focal
Fixed 1.18.0-0ubuntu1.3
18.04 LTS bionic
Fixed 1.14.0-0ubuntu1.10
16.04 LTS xenial
Fixed 1.10.3-0ubuntu0.16.04.5+esm3
14.04 LTS trusty
Vulnerable
sendmail 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 Ignored end of life, was needed
22.04 LTS jammy
Vulnerable
21.10 impish Ignored end of life
21.04 hirsute Ignored end of life
20.04 LTS focal
Vulnerable
18.04 LTS bionic
Vulnerable
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty
Vulnerable
vsftpd 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 Ignored end of life
21.04 hirsute Ignored end of life
20.04 LTS focal
Fixed 3.0.5-0ubuntu0.20.04.1
18.04 LTS bionic
Vulnerable
16.04 LTS xenial
Vulnerable
14.04 LTS trusty
Vulnerable

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Notes

mdeslaur

the mail proxy mechanisms aren't included in nginx.conf by default

Patch details

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

Package Patch details
nginx

Severity score breakdown

Parameter Value
Base score 7.4 · High
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact None
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References

Related Ubuntu Security Notices (USN)

Other references