{"id":"CVE-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-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.","aliases":["GHSA-vwhj-3g83-v276"],"modified":"2026-08-12T04:24:51.972864397Z","published":"2026-08-10T21:19:02.908Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72916.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-1286","CWE-918"]},"references":[{"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":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72916.json"},{"type":"ADVISORY","url":"https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72916"},{"type":"FIX","url":"https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892"},{"type":"FIX","url":"https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074"},{"type":"FIX","url":"https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b"},{"type":"FIX","url":"https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mastodon/mastodon","events":[{"introduced":"0"},{"introduced":"5a8ab0a3e62a8825e28bb74c1760ba6488d20c97"},{"introduced":"52aa8a44bbd0c9a6673cbd9b7c088020be938799"},{"fixed":"da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d"},{"fixed":"18c61f286f1f5718a8f517940ba384866ffa3892"},{"fixed":"930aa9fee26bf9eaefe27826fa1061288d83373b"},{"fixed":"467c933459c7d0e5513475b9e4888afaedfb1074"},{"fixed":"827f63a8fe976e07921ab0f5c9fcca8420c56858"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0"},{"fixed":"4.4.21"},{"introduced":"4.5.0-beta.1"},{"fixed":"4.5.14"},{"introduced":"4.6.0-beta.1"},{"fixed":"4.6.4"}]}}],"versions":["v4.4.20","v4.5.13","v4.6.3","v4.6.2","v4.4.19","v4.5.12","v4.6.1","v4.6.0","v4.6.0-rc.2","v4.6.0-rc.1","v4.6.0-beta.1","v4.5.11","v4.4.18","v4.4.17","v4.5.10","v4.4.16","v4.5.9","v4.4.15","v4.5.8","v4.4.14","v4.5.7","v4.5.6","v4.4.13","v4.4.12","v4.5.5","v4.5.4","v4.4.11","v4.5.3","v4.4.10","v4.5.2","v4.4.9","v4.5.1","v4.5.0","v4.4.8","v4.5.0-rc.3","v4.5.0-rc.2","v4.5.0-rc.1","v4.5.0-beta.2","v4.4.7","v4.5.0-beta.1","v4.4.6","v4.4.5","v4.4.4","v4.4.3","v4.4.2","v4.4.1","v4.4.0","v4.4.0-rc.1","v4.4.0-beta.2","v4.4.0-beta.1","v4.3.0-rc.1","v4.3.0-beta.2","v4.3.0-beta.1","v4.2.0","v4.2.0-rc2","v4.2.0-rc1","v4.2.0-beta3","v4.2.0-beta2","v4.2.0-beta1","v4.0.2","v4.1.0","v4.1.0rc3","v4.1.0rc2","v4.1.0rc1","v4.0.1","v4.0.0","v4.0.0rc4","v3.5.3","v4.0.0rc3","v4.0.0rc2","v4.0.0rc1","v3.5.2","v3.5.1","v3.5.0","v3.5.0rc3","v3.5.0rc2","v3.5.0rc1","v3.3.0","v3.4.1","v3.4.0","v3.4.0rc2","v3.4.0rc1","v3.3.0rc3","v3.3.0rc2","v3.3.0rc1","v3.2.0","v3.2.0rc2","v3.2.0rc1","v3.1.4","v3.1.3","v3.1.2","v3.0.1","v3.1.1","v3.1.0","v3.1.0rc2","v3.1.0rc1","v3.0.0","v3.0.0rc3","v3.0.0rc2","v3.0.0rc1","v2.9.2","v2.9.1","v2.9.0","v2.9.0rc2","v2.9.0rc1","v2.8.2","v2.8.1","v2.8.0","v2.8.0rc3","v2.8.0rc2","v2.8.0rc1","v2.7.1","v2.7.0","v2.7.0rc3","v2.7.0rc2","v2.7.0rc1","v2.6.1","v2.6.0","v2.6.0rc4","v2.6.0rc3","v2.6.0rc2","v2.6.0rc1","v2.5.0","v2.5.0rc2","v2.5.0rc1","v2.4.3","v2.4.3rc3","v2.4.3rc2","v2.4.3rc1","v2.4.2","v2.4.2rc3","v2.4.2rc2","v2.4.2rc1","v2.4.1","v2.4.1rc4","v2.4.1rc3","v2.4.1rc2","v2.4.1rc1","v2.4.0","v2.4.0rc5","v2.4.0rc4","v2.4.0rc3","v2.4.0rc2","v2.4.0rc1","v2.3.2","v2.3.2rc5","v2.3.2rc4","v2.3.2rc3","v2.3.2rc2","v2.3.2rc1","v2.3.1","v2.3.1rc3","v2.3.1rc2","v2.3.1rc1","v2.3.0","v2.3.0rc3","v2.3.0rc2","v2.3.0rc1","v2.2.0","v2.2.0rc2","v2.2.0rc1","v2.1.3","v2.1.2","v2.1.1","v2.1.0","v2.1.0rc6","v2.1.0rc5","v2.1.0rc4","v2.1.0rc3","v2.1.0rc2","v2.1.0rc1","v2.0.0","v2.0.0rc4","v2.0.0rc3","v2.0.0rc2","v2.0.0rc1","v1.6.1","v1.6.0","v1.6.0rc5","v1.6.0rc4","v1.6.0rc3","v1.6.0rc2","v1.6.0rc1","v1.5.1","v1.5.0","v1.5.0rc3","v1.5.0rc2","v1.5.0rc1","v1.4.7","v1.4.6","v1.4.5","v1.4.4","v1.4.3","v1.4.2","v1.4.1","v1.4rc6","v1.4rc5","v1.4rc4","v1.4rc3","v1.4rc2","v1.4rc1","v1.3.2","v1.3.1","v1.3","v1.2.2","v1.2.1","v1.2","v1.1.2","v1.1.1","v1.1","v1.0","v0.9.9","v0.9","v0.8","v0.7","v0.6","v0.1.2","v0.1.1","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-72916.json"}}],"schema_version":"1.9.0","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"}]}