Vulnerability in Nodebb
CVE-2026-58593
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.003 (19.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 19th percentile — 19.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Nodebb — versions 4.13.2
Weakness classification (CWE)
References
- github.com/bikini/exploitarium/tree/main/nodebb-activitypub-attributedto-local-… (Exploit, Third Party Advisory, exploit)
- github.com/NodeBB/NodeBB/blob/v4.13.2/src/activitypub/mocks.js (Exploit, product, Third Party Advisory)
- www.vulncheck.com/advisories/nodebb-activitypub-author-spoofing-via-unvalidated… (Exploit, Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-58593?
- CVE-2026-58593 is a high-severity vulnerability in Nodebb, classified under Authentication Bypass by Spoofing. CVSS score: 7.5/10. Published 2026-07-01.
- How severe is CVE-2026-58593?
- High severity. CVSS v3 base score is 7.5 out of 10.