{"id":"BIT-mastodon-2026-72916","summary":"Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses","details":"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.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with IPAddr#ipv4_compat?. An attacker could supply an address in the omitted range to bypass the ALLOWED_PRIVATE_ADDRESSES protection and make Mastodon send HTTP requests to loopback interfaces, potentially accessing private resources and services. Exploitation requires a system that supports the obsolete IPv4-compatible IPv6 mechanism. This issue is fixed in versions 4.4.21, 4.5.14, 4.6.4, and 4.7.0.","aliases":["CVE-2026-72916","GHSA-vwhj-3g83-v276"],"modified":"2026-08-17T08:10:42.510102081Z","published":"2026-08-17T05:46:39.602Z","database_specific":{"cpes":["cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*"],"severity":"Medium"},"references":[{"type":"WEB","url":"https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892"},{"type":"WEB","url":"https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074"},{"type":"WEB","url":"https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b"},{"type":"WEB","url":"https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d"},{"type":"WEB","url":"https://github.com/mastodon/mastodon/releases/tag/v4.4.21"},{"type":"WEB","url":"https://github.com/mastodon/mastodon/releases/tag/v4.5.14"},{"type":"WEB","url":"https://github.com/mastodon/mastodon/releases/tag/v4.6.4"},{"type":"WEB","url":"https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1"},{"type":"WEB","url":"https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72916"}],"affected":[{"package":{"name":"mastodon","ecosystem":"Bitnami","purl":"pkg:bitnami/mastodon"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.4.21"},{"introduced":"4.5.0"},{"fixed":"4.5.14"},{"introduced":"4.6.0"},{"fixed":"4.6.4"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/mastodon/BIT-mastodon-2026-72916.json"},"severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"}]}],"schema_version":"1.9.0"}