{"id":"CVE-2026-72916","aliases":["BIT-mastodon-2026-72916","EUVD-2026-55839","GHSA-vwhj-3g83-v276"],"status":"published","title":"Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses","description":"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.","severity":{"version":"4.0","score":6.3,"vector":"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00974,"percentile":0.62546,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1286","CWE-918"],"published":"2026-08-10T21:19:02Z","modified":"2026-10-28T02:30:52Z","fixes":[{"ecosystem":"Bitnami","package":"mastodon","fixed_in":["4.4.21","4.5.14","4.6.4"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Bitnami","package":"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"}]}]}],"products":[{"vendor":"mastodon","product":"mastodon"}],"references":[{"url":"https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276","tags":["x_refsource_CONFIRM","web","advisory"]},{"url":"https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892","tags":["x_refsource_MISC","web","fix"]},{"url":"https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074","tags":["x_refsource_MISC","web","fix"]},{"url":"https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b","tags":["x_refsource_MISC","web","fix"]},{"url":"https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d","tags":["x_refsource_MISC","web","fix"]},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.4.21","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.5.14","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.6.4","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1","tags":["x_refsource_MISC","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72916","tags":["web","advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72916.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-72916","title":"Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses","description":"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.","status":"published","published":"2026-08-10T21:19:02.908Z","modified":"2026-08-13T15:13:23.011Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium","assessor":"cna"}],"cwes":["CWE-918","CWE-1286"],"updated_at":"2026-11-02T14:19:52.016971Z"}],"euvd":[{"id":"EUVD-2026-55839","description":"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.","status":"published","published":"2026-08-10T21:19:02Z","modified":"2026-08-13T15:13:23Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium"}],"updated_at":"2026-11-02T18:01:56.415282Z"}],"nvd":[{"id":"CVE-2026-72916","description":"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.","status":"published","published":"2026-08-10T22:17:10.51Z","modified":"2026-09-09T20:55:04.493Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium","assessor":"secondary"}],"cwes":["CWE-918","CWE-1286"],"updated_at":"2026-11-02T14:12:36.102748Z"}],"osv":[{"id":"CVE-2026-72916","title":"Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses","description":"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.","status":"published","published":"2026-08-10T21:19:02.908Z","modified":"2026-10-28T02:30:52.499359976Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium"}],"cwes":["CWE-1286","CWE-918"],"updated_at":"2026-11-02T15:45:15.88521Z"},{"id":"BIT-mastodon-2026-72916","title":"Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses","description":"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.","status":"published","published":"2026-08-17T05:46:39.602Z","modified":"2026-08-17T08:10:42.510102081Z","updated_at":"2026-11-02T15:28:33.072289Z"}]}}