{"id":"BIT-mastodon-2026-47389","summary":"Mastodon: SSRF protection bypass on older Ruby versions","details":"Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, when using Ruby versions older than 3.4, PrivateAddressCheck.private_address? returns false for IPv4-mapped IPv6 addresses (::ffff:a.b.c.d) corresponding to some private IPv4 addresses, depending on Ruby version, this can include loopback, RFC1918 private networks, and link-local space. An attacker who controls DNS for any domain can publish an AAAA record with such a mapped address; any outbound HTTP fetch Mastodon performs against that hostname then opens a real TCP connection to the underlying IPv4 address, including 127.0.0.1 and cloud-metadata endpoints such as 169.254.169.254. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.","aliases":["CVE-2026-47389","GHSA-xx55-4rrg-8xg6"],"modified":"2026-07-08T08:26:11.119788093Z","published":"2026-07-06T05:55:17.401Z","database_specific":{"severity":"High","cpes":["cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*"]},"references":[{"type":"WEB","url":"https://github.com/mastodon/mastodon/security/advisories/GHSA-xx55-4rrg-8xg6"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47389"}],"affected":[{"package":{"name":"mastodon","ecosystem":"Bitnami","purl":"pkg:bitnami/mastodon"},"ranges":[{"type":"SEMVER","events":[{"introduced":"4.5.0"},{"fixed":"4.5.10"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/mastodon/BIT-mastodon-2026-47389.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N"}]}],"schema_version":"1.7.5"}