CVE-2026-104463: YesWiki before 4.6.7 Unauthenticated SSRF via ActivityPub Inbox
YesWiki before 4.6.7 contains a server-side request forgery vulnerability that allows unauthenticated attackers to trigger server requests by sending signed Follow activities to the public forms actor inbox route. Attackers sign requests with their own keyId while supplying internal actor URLs in the body, reaching internal hosts or cloud metadata via blind GET and POST requests.
Affected Software
Event History
Frequently Asked Questions
What does an attacker need to exploit this issue?
The attacker does not need authentication or user interaction. They need to send a signed ActivityPub Follow activity to the public forms actor inbox route, using their own keyId while placing an internal actor URL in the activity body.
Which systems are exposed?
YesWiki installations before 4.6.7 are affected where the public forms actor inbox route is reachable. The issue can be used to make the YesWiki server send blind GET and POST requests to internal hosts or cloud metadata endpoints.
Is a default deployment affected?
The available information identifies the public forms actor inbox route as the exposed entry point, but does not state whether it is enabled or reachable in every default deployment. Verify whether that route is publicly accessible on the affected instance.
How can I tell whether an instance may have been targeted?
Review logs for incoming signed ActivityPub Follow requests to the public forms actor inbox route, especially requests whose activity body contains internal, loopback, private-network, or cloud metadata actor URLs. Also review outbound traffic from the YesWiki host for unexpected GET or POST requests to internal services.
What can be done while patching is pending?
Restrict public access to the forms actor inbox route if operationally possible, and apply outbound network controls to prevent the YesWiki server from reaching internal networks and cloud metadata services. These measures limit the server-side requests an attacker can induce.