K000132639 : ALPACA: TLS vulnerability CVE-2021-3618

Security Advisory Description

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. (CVE-2021-3618)

Impact

F5 products are not impacted by this vulnerability in the control plane or data plane; however, it is possible to expose your backend systems through the data plane under the following conditions:

• You have a Transport Layer Security (TLS) certificate whose subject or Subject Alternative Name (SAN) is valid for multiple backend service endpoints. For example, a certificate subject containing a wildcard domain name.
• Your configuration includes a wildcard-type forwarding service. For example, a BIG-IP wildcard forwarding virtual server.