{"id":"CVE-2026-63115","aliases":[],"cve":{"records":[{"id":"CVE-2026-63115","source":"GitHub_M","state":"PUBLISHED","reasons":[],"replacements":[],"disputed":false,"unsupportedWhenAssigned":false,"reserved":"2026-07-15T16:54:55.816Z","published":"2026-10-30T21:33:55.894Z","modified":"2026-10-30T21:33:55.894Z"}],"publishers":[{"name":"GitHub_M","role":"CNA","organizationId":"a0819718-46f1-4df5-94e2-005712e83aaa","modified":"2026-10-30T21:33:55.894Z"}],"references":[{"url":"https://github.com/TryGhost/ActivityPub/security/advisories/GHSA-mm4q-93gr-5mwc","tags":["x_refsource_CONFIRM"],"source":"GitHub_M"},{"url":"https://github.com/TryGhost/ActivityPub/pull/1929","tags":["x_refsource_MISC"],"source":"GitHub_M"},{"url":"https://github.com/TryGhost/ActivityPub/commit/1526f540b983da97750b380868a210e6cdfb985e","tags":["x_refsource_MISC"],"source":"GitHub_M"},{"url":"https://github.com/TryGhost/ActivityPub/releases/tag/v1.2.6","tags":["x_refsource_MISC"],"source":"GitHub_M"}],"weaknesses":[{"id":"CWE-290","description":"CWE-290: Authentication Bypass by Spoofing","source":"GitHub_M"},{"id":"CWE-345","description":"CWE-345: Insufficient Verification of Data Authenticity","source":"GitHub_M"},{"id":"CWE-863","description":"CWE-863: Incorrect Authorization","source":"GitHub_M"}],"applicability":[],"prioritization":[]},"title":"ActivityPub Undo handler can unfollow or remove reposts on behalf of other accounts","titleSource":"GitHub_M","descriptionSource":"GitHub_M","description":"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1.2.6.","score":5.3,"severity":"medium","published":"2026-10-30T21:33:55.894Z","modified":"2026-10-30T21:33:55.894Z","withdrawn":false,"knownExploited":false,"affected":[],"products":[{"vendor":"TryGhost","name":"ActivityPub","platforms":[],"versions":[{"version":">= 1.0.0, < 1.2.6","status":"affected"}],"cpes":[],"source":"GitHub_M","url":"https://www.cve.org/CVERecord?id=CVE-2026-63115"}],"remediation":[],"references":["https://github.com/TryGhost/ActivityPub/security/advisories/GHSA-mm4q-93gr-5mwc","https://github.com/TryGhost/ActivityPub/pull/1929","https://github.com/TryGhost/ActivityPub/commit/1526f540b983da97750b380868a210e6cdfb985e","https://github.com/TryGhost/ActivityPub/releases/tag/v1.2.6"],"sources":[{"name":"CVE","id":"CVE-2026-63115","modified":"2026-10-30T21:33:55.894Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-63115"}],"assessments":[{"source":"GitHub_M","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","score":5.3}],"sourceAffected":[],"observedAt":"2026-10-30T22:16:29.189Z","kev":{"status":"not-listed","checkedAt":"2026-10-31T00:40:31.812Z"},"coverage":[{"source":"NVD","status":"not-checked"},{"source":"GHSA","status":"not-checked"},{"source":"EUVD","status":"not-checked"},{"source":"EPSS","status":"not-checked"}],"evidence":[],"aiSummary":null}