PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In version 2.10 and earlier, PJSIP transport can be reused if they have the same IP address + port + protocol. However, this is insufficient for secure transport since it lacks remote hostname authentication. Suppose we have created a TLS connection to sip.foo.com, which has an IP address 100.1.1.1. If we want to create a TLS connection to another hostname, say sip.bar.com, which has the same IP address, then it will reuse that existing connection, even though 100.1.1.1 does not have certificate to authenticate as sip.bar.com. The vulnerability allows for an insecure interaction without user awareness. It affects users who need access to connections to different destinations that translate to the same address, and allows man-in-the-middle attack if attacker can route a connection to another destination such as in the case of DNS spoofing.
The product communicates with a host that provides a certificate, but the product does not properly ensure that the certificate is actually associated with that host.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Pjsip | Teluu | * | 2.10 (including) |
| Pjproject | Ubuntu | bionic | * |
| Pjproject | Ubuntu | trusty | * |
| Pjproject | Ubuntu | xenial | * |
Even if a certificate is well-formed, signed, and follows the chain of trust, it may simply be a valid certificate for a different site than the site that the product is interacting with. If the certificate’s host-specific data is not properly checked - such as the Common Name (CN) in the Subject or the Subject Alternative Name (SAN) extension of an X.509 certificate - it may be possible for a redirection or spoofing attack to allow a malicious host with a valid certificate to provide data, impersonating a trusted host. In order to ensure data integrity, the certificate must be valid and it must pertain to the site that is being accessed. Even if the product attempts to check the hostname, it is still possible to incorrectly check the hostname. For example, attackers could create a certificate with a name that begins with a trusted name followed by a NUL byte, which could cause some string-based comparisons to only examine the portion that contains the trusted name. This weakness can occur even when the product uses Certificate Pinning, if the product does not verify the hostname at the time a certificate is pinned.