high
7.4
CWE
295
Advisory Published
CVE Published
Updated

CVE-2021-3618

First published: Thu Jun 24 2021(Updated: )

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.

Credit: secalert@redhat.com secalert@redhat.com

Affected SoftwareAffected VersionHow to fix
redhat/vsftpd<3.0.4
3.0.4
redhat/nginx<1.21.0
1.21.0
redhat/sendmail<8.17
8.17
ubuntu/nginx<1.14.0-0ubuntu1.10
1.14.0-0ubuntu1.10
ubuntu/nginx<1.18.0-0ubuntu1.3
1.18.0-0ubuntu1.3
ubuntu/nginx<1.21.0
1.21.0
ubuntu/nginx<1.10.3-0ubuntu0.16.04.5+
1.10.3-0ubuntu0.16.04.5+
ubuntu/nginx<1.18.0-6ubuntu11.1
1.18.0-6ubuntu11.1
ubuntu/nginx<1.18.0-6ubuntu14.1
1.18.0-6ubuntu14.1
ubuntu/sendmail<8.16.1-1
8.16.1-1
ubuntu/vsftpd<3.0.4
3.0.4
ubuntu/vsftpd<3.0.5-0ubuntu0.20.04.1
3.0.5-0ubuntu0.20.04.1
<1.21.0
<8.17
<3.0.4
=33
=34
=35
=10.0
F5 Nginx<1.21.0
Sendmail Sendmail<8.17
Vsftpd Project Vsftpd<3.0.4
Fedoraproject Fedora=33
Fedoraproject Fedora=34
Fedoraproject Fedora=35
Debian Debian Linux=10.0
debian/nginx<=1.14.2-2+deb10u4
1.14.2-2+deb10u5
1.18.0-6.1+deb11u3
1.22.1-9
1.24.0-2
debian/sendmail<=8.15.2-14~deb10u1<=8.15.2-22
8.17.1.9-2
8.17.2-1
debian/vsftpd<=3.0.3-12<=3.0.3-13

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Reference Links

Parent vulnerabilities

(Appears in the following advisories)

Frequently Asked Questions

  • What is ALPACA vulnerability (CVE-2021-3618)?

    ALPACA is an application layer protocol content confusion attack that exploits TLS servers implementing different protocols but using compatible certificates.

  • What is the severity of CVE-2021-3618?

    The severity of CVE-2021-3618 is medium.

  • Which software is affected by CVE-2021-3618?

    The software affected by CVE-2021-3618 include nginx, sendmail, and vsftpd.

  • How do I fix CVE-2021-3618 on Debian?

    To fix CVE-2021-3618 on Debian, update the affected software to the specified versions: nginx (1.14.2-2+deb10u5, 1.18.0-6.1+deb11u3, 1.22.1-9, 1.24.0-1), sendmail (8.17.1.9-2, 8.17.2-1).

  • How do I fix CVE-2021-3618 on Red Hat?

    To fix CVE-2021-3618 on Red Hat, update the affected software to the specified versions: nginx (1.21.0), sendmail (8.17), vsftpd (3.0.4).

  • How do I fix CVE-2021-3618 on Ubuntu?

    To fix CVE-2021-3618 on Ubuntu, update the affected software to the specified versions: nginx (upstream: 1.21.0, bionic: 1.14.0-0ubuntu1.10, focal: 1.18.0-0ubuntu1.3, xenial: 1.10.3-0ubuntu0.16.04.5+, impish: 1.18.0-6ubuntu11.1, jammy: 1.18.0-6ubuntu14.1), sendmail (upstream: 8.16.1-1), vsftpd (upstream: 3.0.4, focal: 3.0.5-0ubuntu0.20.04.1).

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