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CVE-2021-3618

Published: 23 March 2022

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.

Notes

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

Priority

Low

Cvss 3 Severity Score

7.4

Score breakdown

Status

Package Release Status
nginx
Launchpad, Ubuntu, Debian
lunar Not vulnerable
(1.22.0-1ubuntu1)
upstream
Released (1.21.0)
bionic
Released (1.14.0-0ubuntu1.10)
focal
Released (1.18.0-0ubuntu1.3)
trusty Needed

xenial
Released (1.10.3-0ubuntu0.16.04.5+esm3)
Available with Ubuntu Pro or Ubuntu Pro (Infra-only)
impish
Released (1.18.0-6ubuntu11.1)
hirsute Ignored
(end of life)
kinetic Ignored
(end of life, was needed)
jammy
Released (1.18.0-6ubuntu14.1)
Patches:
upstream: http://hg.nginx.org/nginx/rev/ec1071830799
sendmail
Launchpad, Ubuntu, Debian
impish Ignored
(end of life)
jammy Needed

lunar Not vulnerable
(8.17.1.9-1)
hirsute Ignored
(end of life)
bionic Needed

focal Needed

trusty Needed

upstream
Released (8.16.1-1)
kinetic Ignored
(end of life, was needed)
xenial Needs triage

vsftpd
Launchpad, Ubuntu, Debian
kinetic Not vulnerable
(3.0.5-0ubuntu1)
lunar Not vulnerable
(3.0.5-0ubuntu1)
upstream
Released (3.0.4)
impish Ignored
(end of life)
hirsute Ignored
(end of life)
bionic Needed

trusty Needed

xenial Needed

focal
Released (3.0.5-0ubuntu0.20.04.1)
jammy Not vulnerable
(3.0.5-0ubuntu1)

Severity score breakdown

Parameter Value
Base score 7.4
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