{"id":"CVE-2026-58593","summary":"NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User","details":"NodeBB does not bind the claimed author of an inbound ActivityPub object to the authenticated remote actor. The inbound middleware verifies the HTTP-signature actor and checks the origin of object.id, but never validates that attributedTo corresponds to the sender. In the object mock, attributedTo is used directly as a uid, and actors.assert silently ignores numeric identifiers (filtering them out without re-deriving the uid), so a federated remote actor can set attributedTo to a bare numeric value such as 1 and have the resulting post or private message created with that local uid as author, including the administrator account. This lets a remote attacker forge posts and direct messages attributed to arbitrary local users. Requires the ActivityPub/federation feature to be enabled.","modified":"2026-08-12T03:51:12.593754784Z","published":"2026-07-01T19:27:23.367Z","database_specific":{"cwe_ids":["CWE-290","CWE-345"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/58xxx/CVE-2026-58593.json","cna_assigner":"VulnCheck"},"references":[{"type":"WEB","url":"https://github.com/NodeBB/NodeBB/blob/v4.13.2/src/activitypub/mocks.js"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/58xxx/CVE-2026-58593.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-58593"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/nodebb-activitypub-author-spoofing-via-unvalidated-attributedto-mapped-to-local-user"},{"type":"EVIDENCE","url":"https://github.com/bikini/exploitarium/tree/main/nodebb-activitypub-attributedto-local-uid-spoof-poc"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/nodebb/nodebb","events":[{"introduced":"c17e7102fb6abcc25d346efa2600fcbbbee9ab04"},{"last_affected":"c17e7102fb6abcc25d346efa2600fcbbbee9ab04"}],"database_specific":{"source":["AFFECTED_FIELD","CPE_RANGE"],"cpe":"cpe:2.3:a:nodebb:nodebb:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"4.13.2"},{"last_affected":"4.13.2"},{"introduced":"0"}]}}],"versions":["4.13.2","v4.13.2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-58593.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"}]}