Vulnerability · Published Jul 1, 2026 · Assigned by VulnCheck

CVE-2026-58593NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User

High 7.5

In plain English

A high-severity insufficient verification of data authenticity in NodeBB from NodeBB. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.3%top 78.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

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.

Affected products (as reported)

Vendor	Product	Versions
NodeBB	NodeBB	4.13.2

Weakness: CWE-345, CWE-290 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References

Proof of Concept exploit
Affected source product
VulnCheck Advisory: NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User third-party-advisory