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 victims 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.
Weakness
The product does not validate, or incorrectly validates, a certificate.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Nginx | F5 | * | 1.21.0 (excluding) |
| Nginx | Ubuntu | bionic | * |
| Nginx | Ubuntu | esm-infra-legacy/trusty | * |
| Nginx | Ubuntu | esm-infra/bionic | * |
| Nginx | Ubuntu | esm-infra/focal | * |
| Nginx | Ubuntu | esm-infra/xenial | * |
| Nginx | Ubuntu | focal | * |
| Nginx | Ubuntu | hirsute | * |
| Nginx | Ubuntu | impish | * |
| Nginx | Ubuntu | jammy | * |
| Nginx | Ubuntu | kinetic | * |
| Nginx | Ubuntu | trusty | * |
| Nginx | Ubuntu | trusty/esm | * |
| Nginx | Ubuntu | upstream | * |
| Nginx | Ubuntu | xenial | * |
| Sendmail | Ubuntu | bionic | * |
| Sendmail | Ubuntu | esm-apps/bionic | * |
| Sendmail | Ubuntu | esm-apps/focal | * |
| Sendmail | Ubuntu | esm-apps/jammy | * |
| Sendmail | Ubuntu | esm-infra-legacy/trusty | * |
| Sendmail | Ubuntu | focal | * |
| Sendmail | Ubuntu | hirsute | * |
| Sendmail | Ubuntu | impish | * |
| Sendmail | Ubuntu | jammy | * |
| Sendmail | Ubuntu | kinetic | * |
| Sendmail | Ubuntu | trusty | * |
| Sendmail | Ubuntu | trusty/esm | * |
| Sendmail | Ubuntu | upstream | * |
| Sendmail | Ubuntu | xenial | * |
| Vsftpd | Ubuntu | bionic | * |
| Vsftpd | Ubuntu | esm-infra-legacy/trusty | * |
| Vsftpd | Ubuntu | esm-infra/bionic | * |
| Vsftpd | Ubuntu | esm-infra/focal | * |
| Vsftpd | Ubuntu | esm-infra/xenial | * |
| Vsftpd | Ubuntu | focal | * |
| Vsftpd | Ubuntu | hirsute | * |
| Vsftpd | Ubuntu | impish | * |
| Vsftpd | Ubuntu | trusty | * |
| Vsftpd | Ubuntu | trusty/esm | * |
| Vsftpd | Ubuntu | upstream | * |
| Vsftpd | Ubuntu | xenial | * |