{"id":"CVE-2026-50128","summary":"Mastodon: Spoofing of attribution domains","details":"Mastodon is a free, open-source social network server based on ActivityPub. From 4.3.0 until 4.5.11 and 4.4.18, Mastodon has a feature to let websites credit authors of their articles. To prevent false attribution claims, Mastodon uses the attributionDomains JSON-LD term, however, an error in how it is defined makes Linked Data Signatures on the toot:attributionDomains property ineffective. An attacker can arbitrarily modify the attributionDomains value of a legitimately signed Update activity and bypass Mastodon’s signature verification. This vulnerability is fixed in 4.5.11 and 4.4.18.","aliases":["BIT-mastodon-2026-50128"],"modified":"2026-07-15T01:49:02.209953141Z","published":"2026-06-24T19:48:52.942Z","related":["GHSA-pwx3-qcgw-vh7h","GHSA-rwcw-vq68-g34p"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-354"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/50xxx/CVE-2026-50128.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/50xxx/CVE-2026-50128.json"},{"type":"ADVISORY","url":"https://github.com/mastodon/mastodon/security/advisories/GHSA-rwcw-vq68-g34p"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-50128"},{"type":"EVIDENCE","url":"https://github.com/gogs/gogs/security/advisories/GHSA-pwx3-qcgw-vh7h"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mastodon/mastodon","events":[{"introduced":"5a8ab0a3e62a8825e28bb74c1760ba6488d20c97"},{"fixed":"0748a5ff81b24e666ab10b8ee7fbc6f0362c8cb0"},{"introduced":"ab36c152f9e5f9054798504354365dcaef4e5c43"},{"fixed":"3555d595e2a6fcf425c73f783e8709b1e44c0872"}],"database_specific":{"extracted_events":[{"introduced":"4.5.0-beta.1"},{"fixed":"4.5.11"},{"introduced":"4.3.0"},{"fixed":"4.4.18"}],"source":"AFFECTED_FIELD"}}],"versions":["v4.5.10","v4.5.9","v4.5.8","v4.5.7","v4.5.6","v4.5.5","v4.5.4","v4.5.3","v4.5.2","v4.5.1","v4.5.0","v4.5.0-rc.3","v4.5.0-rc.2","v4.5.0-rc.1","v4.5.0-beta.2","v4.5.0-beta.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-50128.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}