{"id":"CVE-2026-58593","aliases":["EUVD-2026-41131","GHSA-8m27-grg5-27vj"],"status":"published","title":"NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User","description":"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.","severity":{"version":"4.0","score":8.7,"vector":"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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.0029,"percentile":0.21719,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-290","CWE-345"],"published":"2026-07-01T19:27:23Z","modified":"2026-10-28T02:30:23Z","products":[{"vendor":"nodebb","product":"nodebb"}],"references":[{"url":"https://github.com/bikini/exploitarium/tree/main/nodebb-activitypub-attributedto-local-uid-spoof-poc","tags":["exploit","Exploit","Third Party Advisory","evidence"]},{"url":"https://github.com/NodeBB/NodeBB/blob/v4.13.2/src/activitypub/mocks.js","tags":["product","Exploit","Third Party Advisory","web"]},{"url":"https://www.vulncheck.com/advisories/nodebb-activitypub-author-spoofing-via-unvalidated-attributedto-mapped-to-local-user","tags":["third-party-advisory","Exploit","Third Party Advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-58593","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-8m27-grg5-27vj"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/58xxx/CVE-2026-58593.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-58593","title":"NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User","description":"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.","status":"published","published":"2026-07-01T19:27:23.367Z","modified":"2026-07-07T12:50:17.73Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high","assessor":"cna"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"cna"}],"cwes":["CWE-345","CWE-290"],"updated_at":"2026-11-02T13:47:39.876248Z"}],"euvd":[{"id":"EUVD-2026-41131","description":"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.","status":"published","published":"2026-07-01T19:27:23Z","modified":"2026-07-07T12:50:17Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"updated_at":"2026-11-02T18:20:12.41351Z"}],"ghsa":[{"id":"GHSA-8m27-grg5-27vj","title":"NodeBB does not bind the claimed author of an inbound ActivityPub object to the authenticated...","description":"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.","status":"published","published":"2026-07-01T21:36:20Z","modified":"2026-07-01T21:36:26Z","cvss":[{"version":"4.0","score":8.7,"vector":"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/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":"high"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"cwes":["CWE-290"],"updated_at":"2026-11-02T15:09:10.245383Z"}],"nvd":[{"id":"CVE-2026-58593","description":"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.","status":"published","published":"2026-07-01T20:17:11.75Z","modified":"2026-07-07T13:16:32.19Z","cvss":[{"version":"4.0","score":8.7,"vector":"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/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":"high","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"secondary"}],"cwes":["CWE-290","CWE-345"],"updated_at":"2026-11-02T14:12:27.199837Z"}],"osv":[{"id":"CVE-2026-58593","title":"NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User","description":"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.","status":"published","published":"2026-07-01T19:27:23.367Z","modified":"2026-10-28T02:30:23.383695307Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"cwes":["CWE-290","CWE-345"],"updated_at":"2026-11-02T15:45:12.496548Z"}]}}