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 Software | Affected Version | How to fix |
|---|---|---|
| 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 | |
| redhat/vsftpd | <3.0.4 | 3.0.4 |
| redhat/nginx | <1.21.0 | 1.21.0 |
| redhat/sendmail | <8.17 | 8.17 |
| debian/nginx | 1.18.0-6.1+deb11u3 1.22.1-9 1.26.0-3 | |
| debian/sendmail | <=8.15.2-22+deb11u3 | 8.17.1.9-2+deb12u2 8.18.1-6 |
| debian/vsftpd | <=3.0.3-12<=3.0.3-13<=3.0.3-13.1 |
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Reference Links
- https://alpaca-attack.com/
- https://bugzilla.redhat.com/show_bug.cgi?id=1975623
- https://lists.debian.org/debian-lts-announce/2022/11/msg00031.html
- https://launchpad.net/bugs/cve/CVE-2021-3618
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1975648
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1975652
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1975653
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1975651
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1975650
- http://hg.nginx.org/nginx/rev/ec1071830799
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1975623#c37
- https://security.appspot.com/vsftpd/Changelog.txt
- https://marc.info/?l=sendmail-announce&m=159394546814125&w=2
- https://lists.exim.org/lurker/message/20210609.200324.f0e073ed.el.html
- https://security-tracker.debian.org/tracker/CVE-2021-3618
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-3618
- https://nvd.nist.gov/vuln/detail/CVE-2021-3618
- https://ubuntu.com/security/CVE-2021-3618
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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