Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Nodebb | Nodebb | <= 4.13.2 |
Related Weaknesses (CWE)
References
- https://github.com/NodeBB/NodeBB/blob/v4.13.2/src/activitypub/mocks.jsExploitThird Party Advisory
- https://github.com/bikini/exploitarium/tree/main/nodebb-activitypub-attributedtoExploitThird Party Advisory
- https://www.vulncheck.com/advisories/nodebb-activitypub-author-spoofing-via-unvaExploitThird Party Advisory
FAQ
What is CVE-2026-58593?
CVE-2026-58593 is a vulnerability with a CVSS score of 7.5 (HIGH). 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,...
How severe is CVE-2026-58593?
CVE-2026-58593 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-58593?
Check the references section above for vendor advisories and patch information. Affected products include: Nodebb Nodebb.