{"id":"CVE-2026-72916","state":"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.","publishedAt":"2026-08-10T21:19:02.908Z","updatedAt":"2026-08-13T15:13:23.011Z","severity":{"score":6.3,"label":"Medium","version":"4.0","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","source":"GitHub_M"},"assigner":"GitHub_M","products":["mastodon mastodon"],"affected":[{"vendor":"mastodon","product":"mastodon","versions":[{"version":"< 4.4.21","status":"affected"},{"version":">= 4.5.0-beta.1, < 4.5.14","status":"affected"},{"version":">= 4.6.0-beta.1, < 4.6.4","status":"affected"}]}],"references":["https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276","https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892","https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074","https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b","https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d","https://github.com/mastodon/mastodon/releases/tag/v4.4.21","https://github.com/mastodon/mastodon/releases/tag/v4.5.14","https://github.com/mastodon/mastodon/releases/tag/v4.6.4","https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1"],"weaknesses":["CWE-918","CWE-1286"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72916.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72916","state":"PUBLISHED","datePublished":"2026-08-10T21:19:02.908Z","dateUpdated":"2026-08-13T15:13:23.011Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-08-10T17:57:26.143Z"},"containers":{"cna":{"title":"Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"mastodon","product":"mastodon","versions":[{"version":"< 4.4.21","status":"affected"},{"version":">= 4.5.0-beta.1, < 4.5.14","status":"affected"},{"version":">= 4.6.0-beta.1, < 4.6.4","status":"affected"}]}],"references":[{"url":"https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276","name":"https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892","name":"https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892","tags":["x_refsource_MISC"]},{"url":"https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074","name":"https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074","tags":["x_refsource_MISC"]},{"url":"https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b","name":"https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b","tags":["x_refsource_MISC"]},{"url":"https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d","name":"https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d","tags":["x_refsource_MISC"]},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.4.21","name":"https://github.com/mastodon/mastodon/releases/tag/v4.4.21","tags":["x_refsource_MISC"]},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.5.14","name":"https://github.com/mastodon/mastodon/releases/tag/v4.5.14","tags":["x_refsource_MISC"]},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.6.4","name":"https://github.com/mastodon/mastodon/releases/tag/v4.6.4","tags":["x_refsource_MISC"]},{"url":"https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1","name":"https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"HIGH","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"LOW","subAvailabilityImpact":"LOW","baseScore":6.3,"baseSeverity":"MEDIUM","vectorString":"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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-918","lang":"en","description":"CWE-918: Server-Side Request Forgery (SSRF)","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1286","lang":"en","description":"CWE-1286: Improper Validation of Syntactic Correctness of Input","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-10T21:19:02.908Z"},"source":{"advisory":"GHSA-vwhj-3g83-v276","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-13T15:13:13.639949Z","id":"CVE-2026-72916","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-13T15:13:23.011Z"}}]}}}