Curl before 7.49.1 in Apple OS X before macOS Sierra prior to 10.12 allows remote or local attackers to execute arbitrary code, gain sensitive information, cause denial-of-service conditions, bypass security restrictions, and perform unauthorized actions. This may aid in other attacks.
A non-privileged user or program can put code and a config file in a known non-privileged path (under C:/usr/local/) that will make curl <= 7.65.1 automatically run the code (as an openssl "engine") on invocation. If that curl is invoked by a privileged user it can do anything it wants.
Curl versions 7.14.1 through 7.61.1 are vulnerable to a heap-based buffer over-read in the tool_msgs.c:voutf() function that may result in information exposure and denial of service.
A flaw was found in curl before version 7.51. If cookie state is written into a cookie jar file that is later read back and used for subsequent requests, a malicious HTTP server can inject new cookies for arbitrary domains into said cookie jar.
A flaw was found in curl before version 7.51.0 When re-using a connection, curl was doing case insensitive comparisons of user name and password with the existing connections. This means that if an unused connection with proper credentials exists for a protocol that has connection-scoped credentials, an attacker can cause that connection to be reused if s/he knows the case-insensitive version of the correct password.
A flaw was found in curl before version 7.51.0. The way curl handles cookies permits other threads to trigger a use-after-free leading to information disclosure.