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Vulnerability · Published Mar 23, 2022 · Assigned by redhat

CVE-2021-3618

High 7.4

In plain English

A high-severity improper certificate validation in ALPACA. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 2.0% (higher than 81% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS NVD)7.4High
Exploit odds (30 days)2.0%top 18.9% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.20nginx1.20.1-r1ALPINE-CVE-2021-3618
Alpine:v3.21nginx1.20.1-r1ALPINE-CVE-2021-3618
Alpine:v3.22nginx1.20.1-r1ALPINE-CVE-2021-3618
Alpine:v3.23nginx1.20.1-r1ALPINE-CVE-2021-3618
Alpine:v3.24nginx1.20.1-r1ALPINE-CVE-2021-3618
Debian:12nginx1.20.2-2DEBIAN-CVE-2021-3618
Debian:13nginx1.20.2-2DEBIAN-CVE-2021-3618
Debian:14nginx1.20.2-2DEBIAN-CVE-2021-3618
Debian:12sendmail8.16.1-2DEBIAN-CVE-2021-3618
Debian:13sendmail8.16.1-2DEBIAN-CVE-2021-3618
Debian:14sendmail8.16.1-2DEBIAN-CVE-2021-3618
Debian:12vsftpdno fix listedDEBIAN-CVE-2021-3618
Debian:13vsftpd3.0.5-0.1DEBIAN-CVE-2021-3618
Debian:14vsftpd3.0.5-0.1DEBIAN-CVE-2021-3618
Ubuntu:22.04:LTSnginx1.18.0-6ubuntu14.1USN-5371-2
Ubuntu:22.04:LTSnginx1.18.0-6ubuntu14.1UBUNTU-CVE-2021-3618
Ubuntu:22.04:LTSsendmailno fix listedUBUNTU-CVE-2021-3618

Affected products (as reported)

VendorProductVersions
n/a ALPACA vsftpd 3.0.4, nginx 1.21.0, sendmail 8.17

Weakness: CWE-295

References