Vulnerability in F5 nginx
CVE-2021-3618
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.
Vulnerability class: Improper Certificate Validation
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.020 (80.7th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 81st percentile — 80.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.020 · newest: 0.020 · change: -0.000
Affected products
- F5 nginx
- Sendmail
- Vsftpd Project
- Debian Linux — versions 10.0
- Fedoraproject Fedora — versions 33, 34, 35
- Alpaca — versions vsftpd 3.0.4, nginx 1.21.0, sendmail 8.17
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.redhat.com/show_bug.cgi (Patch, Third Party Advisory, Issue Tracking)
- alpaca-attack.com/ (Third Party Advisory)
- lists.debian.org/debian-lts-announce/2022/11/msg00031.html (mailing-list, Mailing List, Third Party Advisory)
Frequently asked questions
- What is CVE-2021-3618?
- CVE-2021-3618 is a high-severity vulnerability in F5 nginx, classified under Improper Certificate Validation. CVSS score: 7.4/10. Published 2022-03-23.
- How severe is CVE-2021-3618?
- High severity. CVSS v3 base score is 7.4 out of 10.
- Is CVE-2021-3618 known to be exploited?
- 9 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.