SiYuan before v3.7.4 Missing Authorization via refreshBacklink

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SiYuan versions before v3.7.4 contain a missing authorization vulnerability in the /api/ref/refreshBacklink endpoint that allows anonymous readers to trigger persistent server-side writes. Attackers can invoke the endpoint with an attacker-controlled block ID to flush transaction queues, scan all references globally, and enqueue database writes, bypassing read-only protections and enabling resource amplification attacks.

Source published

14 Aug 2026 11:35:25 UTC

Source modified

17 Aug 2026 16:09:23 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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CVSS 4.0 · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

SiYuan versions before v3.7.4 contain a missing authorization vulnerability in the /api/ref/refreshBacklink endpoint that allows anonymous readers to trigger persistent server-side writes. Attackers can invoke the endpoint with an attacker-controlled block ID to flush transaction queues, scan all references globally, and enqueue database writes, bypassing read-only protections and enabling resource amplification attacks.

Source published

Aug 14, 2026, 11:35:25 AM (timezone not stated)

Source modified

Aug 17, 2026, 4:09:23 PM (timezone not stated)

Saved here

13 Nov 2026 17:03:49 UTC

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EUVD CVSS 4.0 · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

SiYuan versions before v3.7.4 contain a missing authorization vulnerability in the /api/ref/refreshBacklink endpoint that allows anonymous readers to trigger persistent server-side writes. Attackers can invoke the endpoint with an attacker-controlled block ID to flush transaction queues, scan all references globally, and enqueue database writes, bypassing read-only protections and enabling resource amplification attacks.

Source published

14 Aug 2026 12:16:44 UTC

Source modified

26 Aug 2026 16:57:52 UTC

Saved here

25 Oct 2026 15:19:03 UTC

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CVSS 4.0 · [email protected] · Secondary · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Secondary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

**CVE:** This vulnerability corresponds to [CVE-2026-72812](https://nvd.nist.gov/vuln/detail/CVE-2026-72812). ### Summary The `/api/ref/refreshBacklink` endpoint is gated by `CheckAuth` only. Unlike its mutating siblings, it carries no `CheckAdminRole`, no `CheckReadonly`, and no inline reader-role guard so it falls through all three authorization mechanisms the codebase uses to protect write operations. A publish `RoleReader` or the anonymous account when `Publish.Auth.Enable` is `false` can invoke it, forcing the server to flush its pending write-transaction queue, scan all references globally, load and parse referencing trees from disk, and enqueue database writes. This violates the read-only invariant (it writes even in a globally read-only workspace), provides an unauthenticated resource-amplification/DoS primitive, and applies no per-object access check to the caller-supplied ID. ### Details **Route / auth tier.** `router.go`: `Handle("POST", "/api/ref/refreshBacklink", model.CheckAuth, refreshBacklink)`, `CheckAuth` only. `CheckAuth` admits `RoleReader`; the publish proxy forwards port-6808 traffic with a Reader JWT (anonymous account when publish auth is disabled). Anonymous/reader reachable. **Guard fall-through.** SiYuan protects write handlers with one of three mechanisms: route-level `CheckAdminRole` (AV/riff/repo/sync/setting/snippet/notebook mutations), route-level `CheckReadonly` (filetree/block/attr/tag mutations), or an inline `IsReadOnlyRoleContext` check (e.g. `updateEmbedBlock`, `updateRecentDoc*Time`). `refreshBacklink` has none of the three. **Write path reached.** `refreshBacklink` calls `model.RefreshBacklink(id)`: - `FlushTxQueue()` — forces the pending write-transaction queue to disk. - `refreshRefsByDefID(defID)` → `QueryRefsByDefID(defID)` (global scan with encrypted-box fallback loop) → `filesys.LoadTrees(rootIDs)` (disk read and Lute parse of every referencing tree) → `sql.UpdateRefsTreeQueue(tree)` (enqueues DB writes) → ref-count task update. The handler also does not consult `util.ReadOnly`, so it executes its writes even when the workspace is configured globally read-only. **No per-object authorization.** `defID` is attacker-controlled and receives no publish-access or ownership check, so a reader can force a reference reindex of any document, including publish-forbidden/unpublished ones (cross-scope). ### Proof of Concept Reproduced on a local instance (SiYuan running locally, publish mode enabled on port 6808, publish Basic Auth disabled), as an anonymous reader (no token): **Target endpoint executes the full write path:** ``` POST http://127.0.0.1:6808/api/ref/refreshBacklink {"id":"<any block id>"} ``` Returns `{"code":0,"msg":"","data":null}` HTTP 200 the handler ran to completion, flushing the transaction queue and enqueuing ref writes. **Controls: the guarded mutating siblings correctly reject the same anonymous session:** ``` POST http://127.0.0.1:6808/api/tag/renameTag → 403 (CheckAdminRole and CheckReadonly) POST http://127.0.0.1:6808/api/block/foldBlock → 403 POST http://127.0.0.1:6808/api/block/updateEmbedBlock → code 0 no-op (inline IsReadOnlyRoleContext blocks the write) ``` The 200-vs-403 contrast confirms `refreshBacklink` is reachable and executes where its siblings are blocked. ### Impact An anonymous reader (publish mode with auth disabled) or any publish `RoleReader` can: - **Bypass the read-only invariant:** trigger persistent server-side writes (transaction-queue flush and reference reindex), including in a workspace configured globally read-only. - **Amplify resource use without authentication:** each call forces a transaction flush, a global reference scan, and disk read and parse of every referencing tree, with an attacker-controlled `id` and no rate limiting, a DoS primitive. - **Act cross-scope:** `defID` receives no publish-access check, so a reader can force reindexing of documents outside their publish scope. This is an integrity-invariant violation and a resource-amplification vector, not data corruption or injection, the caller cannot control the content of the writes, only trigger them. Impact is integrity-low and availability-low; no confidentiality impact and no attacker-controlled data reaches storage. ### Suggested fix Apply the same guard its mutating siblings use, add `CheckReadonly` (and `CheckAdminRole` if reference refresh is intended to be an authenticated operation) to the route, or an inline `IsReadOnlyRoleContext` check consistent with `updateEmbedBlock`. The endpoint should also honor `util.ReadOnly` and apply a publish-access check to `defID` so a reader cannot force cross-scope reindexing. More broadly, the three-way guard strategy (route middleware vs. inline check vs. none) is what allowed this handler to receive no gate at all; a structural backstop, a role-scoped route group for the mutation surface would prevent recurrence.

Source published

3 Sep 2026 22:23:19 UTC

Source modified

10 Sep 2026 15:25:49 UTC

Saved here

24 Oct 2026 13:19:41 UTC

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GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Publisher rating · MODERATE

## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-wgwx-479j-23vq. This link is maintained to preserve external references. ## Original Description SiYuan versions before v3.7.4 contain a missing authorization vulnerability in the /api/ref/refreshBacklink endpoint that allows anonymous readers to trigger persistent server-side writes. Attackers can invoke the endpoint with an attacker-controlled block ID to flush transaction queues, scan all references globally, and enqueue database writes, bypassing read-only protections and enabling resource amplification attacks.

Source published

14 Aug 2026 12:31:24 UTC

Source modified

3 Sep 2026 22:30:08 UTC

Saved here

24 Oct 2026 13:19:41 UTC

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GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Publisher rating · MODERATE

SiYuan: Missing authorization on refreshBacklink allows anonymous readers to trigger persistent server-side writes and unauthenticated resource amplification (publish mode) in github.com/siyuan-note/siyuan/kernel

Source published

10 Sep 2026 14:48:42 UTC

Source modified

10 Sep 2026 15:15:14 UTC

Saved here

24 Oct 2026 13:19:41 UTC

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OSV · upstream source license applies

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