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CVE-2026-58593 is a high-severity author spoofing vulnerability in NodeBB's ActivityPub federation handling. The flaw exists in inbound ActivityPub object processing, where NodeBB verifies the HTTP-signature actor and checks the origin of object.id, but does not validate that the object's attributedTo field matches the authenticated remote actor. During object handling, attributedTo is used directly as a local user identifier, and actor validation logic silently ignores numeric identifiers instead of re-deriving or rejecting them. As a result, a federated remote actor can supply a bare numeric attributedTo value corresponding to a local account and cause NodeBB to create posts or private messages as that local user, including the administrator.
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No public exploit code observed for this vulnerability.
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10 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A NodeBB federation authentication/impersonation flaw that allows an external federated server to post and send messages as any local account, including the administrator, when federation is enabled.
An authentication bypass and post forgery vulnerability in NodeBB's ActivityPub middleware.
An author spoofing vulnerability in NodeBB's ActivityPub/federation handling that allows a remote attacker to forge posts and direct messages as arbitrary local users, including the administrator, by supplying an unvalidated attributedTo value.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.