BIT-MASTODON-2026-72916 Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0, PrivateAddressCheck.privateaddress? in app/lib/privateaddresscheck.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with...