Improper certificate validation in ALPACA
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- Spoofing
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-295.
Summary
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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | ALPACA | vsftpd 3.0.4, nginx 1.21.0, sendmail 8.17 | — | No fix listed | CNA |
- ALPACA Vendor— Affected vsftpd 3.0.4, nginx 1.21.0, sendmail 8.17 Fixed in — No fix listed CNA
CPE configurations NVD · 7
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:f5:nginx:*:*:*:*:*:*:*:* | before 1.21.0 | Vulnerable | F5 |
| cpe:2.3:a:sendmail:sendmail:*:*:*:*:*:*:*:* | before 8.17 | Vulnerable | Sendmail |
| cpe:2.3:a:vsftpd_project:vsftpd:*:*:*:*:*:*:*:* | before 3.0.4 | Vulnerable | Vsftpd Project |
| cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* | 33 | Vulnerable | Fedoraproject |
| cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* | 34 | Vulnerable | Fedoraproject |
| cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:* | 35 | Vulnerable | Fedoraproject |
| cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* | 10.0 | Vulnerable | Debian |
- cpe:2.3:a:f5:nginx:*:*:*:*:*:*:*:* Versions before 1.21.0 Vulnerable ·F5
- cpe:2.3:a:sendmail:sendmail:*:*:*:*:*:*:*:* Versions before 8.17 Vulnerable ·Sendmail
- cpe:2.3:a:vsftpd_project:vsftpd:*:*:*:*:*:*:*:* Versions before 3.0.4 Vulnerable ·Vsftpd Project
- cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* Versions 33 Vulnerable ·Fedoraproject
- cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* Versions 34 Vulnerable ·Fedoraproject
- cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:* Versions 35 Vulnerable ·Fedoraproject
- cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* Versions 10.0 Vulnerable ·Debian
Remediation
No fixed version listed by the sources yet.
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Ansible Automation Platform 1.2 | Affected | No fix yet |
| Red Hat Ansible Tower 3 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat Software Collections | Affected | No fix planned: Will not fix |
Not affected: 5 products
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat Software Collections
Timeline
- 2026-10-02 Threatist record created from CVE-2021-3618
- 2026-10-03 Alias added: GHSA-r9r5-jxp7-whr4
References
Sources
- CVE-2021-3618 · CVE Program
- CVE-2021-3618 · NVD
- FIRST EPSS
- GHSA-r9r5-jxp7-whr4 · GitHub Advisory Database · CC BY 4.0
- CVE-2021-3618 · Red Hat security data · CC BY 4.0
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