An issue was discovered in RubyGems 2.6 and later through 3.0.2. Since Gem::CommandManager#run calls alert_error without escaping, escape sequence injection is possible. (There are many ways to cause an error.)
An issue was discovered in RubyGems 2.6 and later through 3.0.2. A crafted gem with a multi-line name is not handled correctly. Therefore, an attacker could inject arbitrary code to the stub line of gemspec, which is eval-ed by code in ensure_loadable_spec during the preinstall check.
A Directory Traversal issue was discovered in RubyGems 2.7.6 and later through 3.0.2. Before making new directories or touching files (which now include path-checking code for symlinks), it would delete the target destination. If that destination was hidden behind a symlink, a malicious gem could delete arbitrary files on the user's machine, presuming the attacker could guess at paths. Given how frequently gem is run as sudo, and how predictable paths are on modern systems (/tmp, /usr, etc.), this could likely lead to data loss or an unusable system.
An issue was discovered in Ruby before 2.3.8, 2.4.x before 2.4.5, 2.5.x before 2.5.2, and 2.6.x before 2.6.0-preview3. It does not taint strings that result from unpacking tainted strings with some formats.
An issue was discovered in the OpenSSL library in Ruby before 2.3.8, 2.4.x before 2.4.5, 2.5.x before 2.5.2, and 2.6.x before 2.6.0-preview3. When two OpenSSL::X509::Name objects are compared using ==, depending on the ordering, non-equal objects may return true. When the first argument is one character longer than the second, or the second argument contains a character that is one less than a character in the same position of the first argument, the result of == will be true. This could be leveraged to create an illegitimate certificate that may be accepted as legitimate and then used in signing or encryption operations.