CVE-2026-58593 NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User
Remote attackers can forge posts and messages attributed to arbitrary local users, including admins, by exploiting unvalidated ActivityPub author fields.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-58593?
CVE-2026-58593 is a high-severity missing authorization vulnerability in NodeBB, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-58593?
It affects 1 product.
Products include Nodebb Nodebb.
How do I fix CVE-2026-58593?
No fix has been published for CVE-2026-58593 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-58593 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58593 exists.
Other vulnerabilities in NodeBB
Sources
Also known as GHSA-8m27-grg5-27vj.