CVE-2026-63115: TryGhost ActivityPub · Authentication Bypass by Spoofing
Affects TryGhost ActivityPubSource CVE Database V5
Not known to be exploited · CVSS 5.3 Medium : upgrade to 1.2.6 when convenient.
Data as of 30 Oct 2026, 21:51 UTC
Thin evidence
One scorer or none| CNA (GitHub_M) | CVSS 3.1 | 5.3 |
|---|
- Patch
- Available – fixed in 1.2.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 30 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade TryGhost ActivityPub to 1.2.6.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| TryGhostActivityPub | Affected
| Fixed in
|
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.
References
- github.com/TryGhost/ActivityPub/security/advisories/GHSA-mm4q-93gr-5mwc (opens in a new tab)
- github.com/TryGhost/ActivityPub/pull/1929 (opens in a new tab)
- github.com/TryGhost/ActivityPub/commit/1526f540b983da97750b380868a210e6cdfb985e (opens in a new tab)
- github.com/TryGhost/ActivityPub/releases/tag/v1.2.6 (opens in a new tab)