Attack Chain

1. Attacker authenticates to the SiYuan application, obtaining a JWT that passes CheckAuth. This can be as a publish-service RoleReader (anonymous publish visitor) or a RoleEditor against a workspace where Editor.ReadOnly = true.
2. Attacker sends a POST request to /api/sync/setSyncInterval with a crafted JSON payload containing a malicious interval value (e.g., 30 or 43200).
3. The server receives the request and updates the Conf.Sync.Interval value based on the attacker-provided interval, persisting the change to conf.json via Conf.Save().
4. Attacker sends a POST request to /api/graph/getGraph with a crafted JSON payload containing a malicious graph configuration.
5. The server receives the request and overwrites model.Conf.Graph.Global from the attacker-supplied JSON and persists the entire workspace conf.json.
6. Attacker sends a POST request to /api/search/updateEmbedBlock with a crafted JSON payload, specifying an embed-block ID and malicious content.
7. The server receives the request and updates the blocks table in the SQL database, rewriting the content column for the specified embed-block ID.
8. Other users accessing the SiYuan application will now see the poisoned content when the embedded block is displayed or searched.

Impact

Successful exploitation allows unauthorized users to modify the SiYuan configuration and data, potentially leading to denial-of-service, data corruption, and information disclosure. Specifically, attackers can:

1. Cause a denial-of-service by setting a minimal cloud sync interval (30 seconds), causing excessive battery drain and bandwidth consumption on connected clients.
2. Effectively pause cloud sync by setting a maximal sync interval (43200 seconds), increasing the risk of data divergence.
3. Corrupt graph rendering by providing extreme values for maxBlocks, minRefs, or nodeSize in the /api/graph/getGraph or /api/graph/getLocalGraph endpoints.
4. Poison search results by injecting malicious content into embed blocks via the /api/search/updateEmbedBlock endpoint.
5. Manipulate the admin’s recently-opened-documents list, potentially disclosing information about publish-private notebooks via the updateRecentDoc* endpoints.

Recommendation

• Deploy the Sigma rule “Detect SiYuan Unauthorized Sync Interval Modification” to monitor for unauthorized modifications to the sync interval using the /api/sync/setSyncInterval endpoint.
• Deploy the Sigma rule “Detect SiYuan Unauthorized Graph Configuration Modification” to monitor for unauthorized modifications to the graph configuration using the /api/graph/getGraph endpoint.
• Apply the patch described in the advisory by adding model.CheckAdminRole and model.CheckReadonly to the affected ginServer.Handle calls in kernel/api/router.go to restrict access to these API endpoints to authorized users.
• Monitor web server logs for POST requests to the listed API endpoints (/api/graph/getGraph, /api/graph/getLocalGraph, /api/sync/setSyncInterval, /api/storage/updateRecentDocViewTime, /api/storage/updateRecentDocCloseTime, /api/storage/updateRecentDocOpenTime, /api/storage/batchUpdateRecentDocCloseTime, /api/search/updateEmbedBlock) without corresponding administrative actions.