{"id":"CVE-2026-58593","state":"PUBLISHED","title":"NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User","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.","publishedAt":"2026-07-01T19:27:23.367Z","updatedAt":"2026-07-07T12:50:17.730Z","severity":{"score":8.7,"label":"High","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","source":"VulnCheck"},"assigner":"VulnCheck","products":["NodeBB NodeBB"],"affected":[{"vendor":"NodeBB","product":"NodeBB","defaultStatus":"affected","versions":[{"version":"4.13.2","status":"affected","versionType":"semver"}]}],"references":["https://github.com/bikini/exploitarium/tree/main/nodebb-activitypub-attributedto-local-uid-spoof-poc","https://github.com/NodeBB/NodeBB/blob/v4.13.2/src/activitypub/mocks.js","https://www.vulncheck.com/advisories/nodebb-activitypub-author-spoofing-via-unvalidated-attributedto-mapped-to-local-user"],"weaknesses":["CWE-345","CWE-290"],"ingestedAt":"2026-10-29T20:12:24.861Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/58xxx/CVE-2026-58593.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-58593","state":"PUBLISHED","datePublished":"2026-07-01T19:27:23.367Z","dateUpdated":"2026-07-07T12:50:17.730Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-07-01T17:20:57.549Z"},"containers":{"cna":{"title":"NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User","descriptions":[{"lang":"en","value":"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":[{"vendor":"NodeBB","product":"NodeBB","defaultStatus":"affected","versions":[{"version":"4.13.2","status":"affected","versionType":"semver"}]}],"references":[{"url":"https://github.com/bikini/exploitarium/tree/main/nodebb-activitypub-attributedto-local-uid-spoof-poc","name":"Proof of Concept","tags":["exploit"]},{"url":"https://github.com/NodeBB/NodeBB/blob/v4.13.2/src/activitypub/mocks.js","name":"Affected source","tags":["product"]},{"url":"https://www.vulncheck.com/advisories/nodebb-activitypub-author-spoofing-via-unvalidated-attributedto-mapped-to-local-user","name":"VulnCheck Advisory: NodeBB - ActivityPub Author Spoofing via Unvalidated attributedTo Mapped to Local User","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV3_1":{"attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"HIGH","availabilityImpact":"NONE","version":"3.1","baseSeverity":"HIGH","baseScore":7.5,"vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"}},{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"HIGH","baseScore":8.7,"vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-345","lang":"en","description":"Insufficient Verification of Data Authenticity","type":"CWE"},{"cweId":"CWE-290","lang":"en","description":"Authentication Bypass by Spoofing","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-07-07T12:50:17.730Z"},"datePublic":"2026-07-01T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:nodebb:nodebb:4.13.2:*:*:*:*:*:*:*"}]}]}],"x_generator":{"engine":"vulncheck"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-02T15:08:35.864075Z","id":"CVE-2026-58593","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-02T15:08:41.737Z"}}]}}}