In mbedTLS before 1.3.19, if a malicious peer supplies a certificate with a specially crafted secp224k1 public key, then an attacker can cause the server or client to attempt to free block of memory held on stack. Depending on the platform, this could result in a Denial of Service (client crash) or potentially could be exploited to allow remote code execution with the same privileges as the host application (CVE-2017-2784).
The mbedtls package has been updated to version 1.3.19, fixing this issue as well as other security issues and bugs.