The Recurly Client Ruby Library before 2.0.13, 2.1.11, 2.2.5, 2.3.10, 2.4.11, 2.5.4, 2.6.3, 2.7.8, 2.8.2, 2.9.2, 2.10.4, 2.11.3 is vulnerable to a Server-Side Request Forgery vulnerability in the "Resource#find" method that could result in compromise of API keys or other critical resources.

The decode method in the OpenSSL::ASN1 module in Ruby before 2.2.8, 2.3.x before 2.3.5, and 2.4.x through 2.4.1 allows attackers to cause a denial of service (interpreter crash) via a crafted string.

The Basic authentication code in WEBrick library in Ruby before 2.2.8, 2.3.x before 2.3.5, and 2.4.x through 2.4.1 allows remote attackers to inject terminal emulator escape sequences into its log and possibly execute arbitrary commands via a crafted user name.

Ruby before 2.4.2, 2.3.5, and 2.2.8 is vulnerable to a malicious format string which contains a precious specifier (*) with a huge minus value. Such situation can lead to a buffer overrun, resulting in a heap memory corruption or an information disclosure from the heap.

Ruby through 2.2.7, 2.3.x through 2.3.4, and 2.4.x through 2.4.1 can expose arbitrary memory during a JSON.generate call. The issues lies in using strdup in ext/json/ext/generator/generator.c, which will stop after encountering a '\0' byte, returning a pointer to a string of length zero, which is not the length stored in space_len.

The parse_char_class function in regparse.c in the Onigmo (aka Oniguruma-mod) regular expression library, as used in Ruby 2.4.0, allows remote attackers to cause a denial of service (deep recursion and application crash) via a crafted regular expression.

RubyGems 2.0.x before 2.0.16, 2.2.x before 2.2.4, and 2.4.x before 2.4.7 does not validate the hostname when fetching gems or making API requests, which allows remote attackers to redirect requests to arbitrary domains via a crafted DNS SRV record, aka a "DNS hijack attack."