{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63115","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-07-15T16:54:55.816Z","datePublished":"2026-10-30T21:33:55.894Z","dateUpdated":"2026-10-30T21:33:55.894Z"},"containers":{"cna":{"title":"ActivityPub Undo handler can unfollow or remove reposts on behalf of other accounts","problemTypes":[{"descriptions":[{"cweId":"CWE-290","lang":"en","description":"CWE-290: Authentication Bypass by Spoofing","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-345","lang":"en","description":"CWE-345: Insufficient Verification of Data Authenticity","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-863","lang":"en","description":"CWE-863: Incorrect Authorization","type":"CWE"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":5.3,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","version":"3.1"}}],"references":[{"name":"https://github.com/TryGhost/ActivityPub/security/advisories/GHSA-mm4q-93gr-5mwc","tags":["x_refsource_CONFIRM"],"url":"https://github.com/TryGhost/ActivityPub/security/advisories/GHSA-mm4q-93gr-5mwc"},{"name":"https://github.com/TryGhost/ActivityPub/pull/1929","tags":["x_refsource_MISC"],"url":"https://github.com/TryGhost/ActivityPub/pull/1929"},{"name":"https://github.com/TryGhost/ActivityPub/commit/1526f540b983da97750b380868a210e6cdfb985e","tags":["x_refsource_MISC"],"url":"https://github.com/TryGhost/ActivityPub/commit/1526f540b983da97750b380868a210e6cdfb985e"},{"name":"https://github.com/TryGhost/ActivityPub/releases/tag/v1.2.6","tags":["x_refsource_MISC"],"url":"https://github.com/TryGhost/ActivityPub/releases/tag/v1.2.6"}],"affected":[{"vendor":"TryGhost","product":"ActivityPub","versions":[{"version":">= 1.0.0, < 1.2.6","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-10-30T21:33:55.894Z"},"descriptions":[{"lang":"en","value":"ActivityPub is a multi-tenant ActivityPub server for Ghost, built with Fedify. From 1.0.0 until 1.2.6, the `Undo` handler allows a remote federated server to cause the service to act on a `follow` or `repost` as though the activity came from a different account. This permits removal of an existing `follow` relationship or `repost` belonging to another account without that account's involvement. No private data is exposed and content is not modified; the affected relationships can be re-established. Services proxying to Ghost's hosted ActivityPub server have already been updated, while self-hosted services require an updated image and redeployment. This issue is fixed in version 1.2.6."}],"source":{"advisory":"GHSA-mm4q-93gr-5mwc","discovery":"UNKNOWN"}}}}