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.
Fix
Nothing published yet: no patch, vendor advisory or mitigation reference on NVD, no vendor advisory in the News for this CVE, not in CISA's KEV, no fixed package version. BaselineWatch does not guess at one.
Change history 1
- First seenCVSS 5.3 · tryghostNVD modified 2026-10-30 21:33
Affected (CPE criteria) 0
NVD has not attached CPE configurations yet.
References 4
- https://github.com/TryGhost/ActivityPub/security/advisories/GHSA-mm4q-93gr-5mwc x_refsource_confirm
- https://github.com/TryGhost/ActivityPub/pull/1929 x_refsource_misc
- https://github.com/TryGhost/ActivityPub/commit/1526f540b983da97750b380868a210e6cdfb985e x_refsource_misc
- https://github.com/TryGhost/ActivityPub/releases/tag/v1.2.6 x_refsource_misc