RubyGems version 2.6.12 and earlier is vulnerable to a DNS hijacking vulnerability that allows a MITM attacker to force the RubyGems client to download and install gems from a server that the attacker controls.

RubyGems version 2.6.12 and earlier fails to validate specification names, allowing a maliciously crafted gem to potentially overwrite any file on the filesystem.

RubyGems version 2.6.12 and earlier is vulnerable to maliciously crafted gem specifications that include terminal escape characters. Printing the gem specification would execute terminal escape sequences.

RubyGems version 2.6.12 and earlier is vulnerable to maliciously crafted gem specifications to cause a denial of service attack against RubyGems clients who have issued a `query` command.

RubyGems 2.0.x before 2.0.17, 2.2.x before 2.2.5, and 2.4.x before 2.4.8 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 with a domain that is suffixed with the original domain name, aka a "DNS hijack attack." NOTE: this vulnerability exists because to an incomplete fix for CVE-2015-3900.

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."

Algorithmic complexity vulnerability in Gem::Version::VERSION_PATTERN in lib/rubygems/version.rb in RubyGems before 1.8.23.1, 1.8.24 through 1.8.25, 2.0.x before 2.0.8, and 2.1.x before 2.1.0, as used in Ruby 1.9.0 through 2.0.0p247, allows remote attackers to cause a denial of service (CPU consumption) via a crafted gem version that triggers a large amount of backtracking in a regular expression.

Algorithmic complexity vulnerability in Gem::Version::ANCHORED_VERSION_PATTERN in lib/rubygems/version.rb in RubyGems before 1.8.23.2, 1.8.24 through 1.8.26, 2.0.x before 2.0.10, and 2.1.x before 2.1.5, as used in Ruby 1.9.0 through 2.0.0p247, allows remote attackers to cause a denial of service (CPU consumption) via a crafted gem version that triggers a large amount of backtracking in a regular expression. NOTE: this issue is due to an incomplete fix for CVE-2013-4287.

RubyGems before 1.8.23 can redirect HTTPS connections to HTTP, which makes it easier for remote attackers to observe or modify a gem during installation via a man-in-the-middle attack.

RubyGems before 1.8.23 does not verify an SSL certificate, which allows remote attackers to modify a gem during installation via a man-in-the-middle attack.