{"id":"CVE-2026-72916","title":"Mastodon is a free, open-source social network server based on ActivityPub","summary":"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-beta.1, PrivateAddressCheck.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses …","severity":"none","cwe":["CWE-918","CWE-1286"],"published":"2026-08-10","updated":"2026-09-09","sourceUpdated":"2026-09-09T20:55:04.493","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-72916","references":[{"url":"https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892","label":"security-advisories@github.com"},{"url":"https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074","label":"security-advisories@github.com"},{"url":"https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b","label":"security-advisories@github.com"},{"url":"https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d","label":"security-advisories@github.com"},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.4.21","label":"security-advisories@github.com"},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.5.14","label":"security-advisories@github.com"},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.6.4","label":"security-advisories@github.com"},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1","label":"security-advisories@github.com"},{"url":"https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276","label":"security-advisories@github.com"}],"tags":["nvd"],"epss":0.00359,"epssPercentile":0.29763,"ingestedAt":"2026-09-09T21:22:45.526Z","slug":"CVE-2026-72916","body":"## Overview\n\nMastodon 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-beta.1, 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-beta.1.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}