#VU59319 Origin validation error in nginx - CVE-2021-3618

Description

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to a logic error in TLS implementation when handling different protocols but using compatible certificates, such as multi-domain or wildcard certificates. A remote attacker with ability to perform TCP/IP layer MitM attack 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.

This attack technique was dubbed ALPACA (application layer protocol content confusion attack).

Remediation

External links

• https://alpaca-attack.com/
• https://bugzilla.redhat.com/show_bug.cgi?id=1975623
• http://hg.nginx.org/nginx/rev/ec1071830799