SiYuan before v3.8.1 Path Traversal via asset.upload

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

SiYuan before v3.8.1 contains a path traversal vulnerability in the asset.upload MCP tool that accepts arbitrary absolute file paths without workspace boundary validation. Attackers can induce the AI Agent to upload sensitive files such as SSH keys or credentials from outside the workspace into the asset directory through prompt injection.

Source published

28 Aug 2026 10:49:23 UTC

Source modified

31 Aug 2026 18:28:15 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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

CVSS 3.1 · 5.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N

SiYuan before v3.8.1 contains a path traversal vulnerability in the asset.upload MCP tool that accepts arbitrary absolute file paths without workspace boundary validation. Attackers can induce the AI Agent to upload sensitive files such as SSH keys or credentials from outside the workspace into the asset directory through prompt injection.

Source published

Aug 28, 2026, 10:49:23 AM (timezone not stated)

Source modified

Aug 31, 2026, 6:28:15 PM (timezone not stated)

Observed here

9 Nov 2026 15:15:32 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

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

SiYuan before v3.8.1 contains a path traversal vulnerability in the asset.upload MCP tool that accepts arbitrary absolute file paths without workspace boundary validation. Attackers can induce the AI Agent to upload sensitive files such as SSH keys or credentials from outside the workspace into the asset directory through prompt injection.

Source published

28 Aug 2026 12:16:32 UTC

Source modified

31 Aug 2026 19:17:15 UTC

Observed here

25 Oct 2026 16:19:10 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:N/VA:N/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 · 5.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N

# Security Advisory — SiYuan MCP `asset.upload` Reads Arbitrary Absolute File Paths (Workspace Boundary Bypass) | Field | Value | |---|---| | **Disclosed by** | joysinleung (`[email protected]`) | | **Report date** | 2026-08-13 | | **Product** | SiYuan (思源笔记) — `siyuan-note/siyuan` | | **Go module** | `github.com/siyuan-note/siyuan/kernel` | | **Affected versions** | `<= 3.8.0` (latest release at report time; statically confirmed on v3.8.0) | | **Patched versions** | 3.8.1 | | **Component** | `kernel/mcp/tools/asset.go` (`assetUpload`), `kernel/model/upload.go` (`InsertLocalAssets`) | | **Relationship to prior advisory** | **Residual of CVE-2026-66012** (GHSA-cvhv-7xhj-xjp8) MCP remediation. See §Relationship. | | **EPSS (exploitation probability)** | Low. Requires the AI Agent to invoke `asset.upload` and the user to approve the (category-level) confirmation; reachable via prompt-injection of the agent. | | **KEV (CISA Known Exploited)** | No (not listed in CISA KEV at report time). | | **Default-config reachable** | **Partial** — requires the Agent/MCP surface to be configured (admin) and a user approval click; the boundary check itself is entirely absent, so any approved upload reads outside the workspace. | --- ## Summary SiYuan exposes a native MCP tool `asset` → `asset.upload`. Its `files` argument is documented as a **comma-separated list of absolute file paths**. The handler (`kernel/mcp/tools/asset.go:195`) only normalizes each entry with `filepath.Abs(...)` — it performs **no workspace boundary check** (`IsSubPath`) and **no sensitive-path check** (`IsSensitivePath`). The downstream `model.InsertLocalAssets` (`kernel/model/upload.go:97`) then `os.Open`s each path and copies its bytes into the workspace `assets/` directory. Every other AI-plane file primitive in SiYuan is workspace-constrained: - `file` / `unzip` tools resolve paths via `resolvePath` (workspace-relative, escape-proof). `asset.upload` is the **only** AI tool that accepts arbitrary absolute paths with zero boundary validation. An attacker who can steer the Agent (prompt injection) can induce it to upload sensitive files — e.g. `/Users/victim/.ssh/id_rsa`, `~/.aws/credentials`, `/etc/passwd` — into the workspace, from where they are reachable via notes / export / sync. ## Relationship to Prior Advisories - **CVE-2026-66012** (GHSA-cvhv-7xhj-xjp8) remediated the MCP endpoint by requiring `CheckAdminRole` on `/mcp` and adding `refuseToAccess` for `conf/conf.json` in the *file* tool. However, the **`asset.upload` tool was never given a workspace boundary check** — it still accepts and reads any absolute path. This is a **residual boundary omission** from that remediation: the admin gate restricts *who* may call MCP, but does not constrain *which files* `asset.upload` may read. We report it as the unpatched half of the MCP file-surface hardening. ## Affected Version Statically confirmed on the latest release **v3.8.0** (tag `v3.8.0`, commit `251596fc0`): - `kernel/mcp/tools/asset.go:195` `assetUpload`: `abs, _ := filepath.Abs(strings.TrimSpace(f))` — normalization only. - `kernel/model/upload.go:97` `InsertLocalAssets`: iterates the path list and `os.Open(assetAbsPath)` → `writeAssetFile(writePath, ...)` into `assetsDirPath`; the `IsSubPath(assetsDirPath, assetAbsPath)` check at line 130 is **only a dedup guard**, not a boundary limit. No workspace/external restriction is applied. ## Component - `kernel/mcp/tools/asset.go:195` — `assetUpload` (`files` arg → `filepath.Abs` only). - `kernel/model/upload.go:97` — `InsertLocalAssets` (`os.Open` + copy to `assets/`). - Contrast (safe): `kernel/mcp/tools/unzip.go:52` `unzipHandler` uses `resolvePath` (workspace-relative, escape-proof). ## Attack Vector **AI Agent / prompt injection.** Victim lets the Agent process attacker-controlled web/note content → agent is induced to call `asset.upload` with `/Users/victim/.ssh/id_rsa` (or similar) as a `files` entry. The user sees a **category-level** confirmation ("upload asset") that does **not** display the specific source path, so the approval is effectively blind to the actual file being read. Once approved, the file is copied into the workspace and exfiltrated via notes/export/sync. No admin role is required beyond the existing Agent/MCP configuration. ## Proof of Concept ```jsonc // Agent tool call (asset.upload), attacker-influenced files argument: { "id": "<someBlockID>", "files": "/Users/victim/.ssh/id_rsa,/Users/victim/.aws/credentials,/etc/passwd" } ``` Handler flow: 1. `filepath.Abs("/Users/victim/.ssh/id_rsa")` → `/Users/victim/.ssh/id_rsa` (no `IsSubPath`/`IsSensitivePath` rejection). 2. `InsertLocalAssets` → `os.Open` → bytes copied into `<workspace>/data/assets/...`. 3. The private key is now readable via the workspace file API / export / sync. ## Impact Confidentiality breach: arbitrary local file read (including SSH keys, cloud credentials, OS secrets) through the AI plane. Integrity/availability not directly impacted. Severity is moderated by the required user approval step, but the approval dialog does not reveal the real source path, so the user cannot make an informed decision. ## Scope Reachable only when the Agent/MCP surface is configured and the user approves the upload action. The boundary check is absent regardless of config — any approved upload reads outside the workspace. ## Remediation 1. **Add boundary enforcement in `assetUpload`**: reject any entry where `!util.IsSubPath(util.WorkspaceDir, abs)` or `util.IsSensitivePath(abs)` (same checks used elsewhere). 2. **Show the real source path in the confirmation dialog** so the user can make an informed decision (currently the `LocalWrite` gate is action-category based and hides the specific path). 3. Mirror the `resolvePath` workspace-relative constraint already applied to the `file` / `unzip` tools. > Note: patch authored against v3.8.0 source; not compiled into a full SiYuan release build. Provided for the maintainer to validate in CI. --- ## Appendix: Suggested Patch (F10) ```diff diff --git a/kernel/mcp/tools/asset.go b/kernel/mcp/tools/asset.go index aaa..bbb 100644 --- a/kernel/mcp/tools/asset.go +++ b/kernel/mcp/tools/asset.go @@ -195,8 +195,16 @@ func assetUpload(args map[string]any) (CallToolResult, error) { fileList := strings.Split(filesStr, ",") for i, f := range fileList { abs, err := filepath.Abs(strings.TrimSpace(f)) - if err != nil { + if err != nil { return CallToolResult{}, err } + // 边界校验：仅允许工作区内的资产，拒绝任意绝对路径越界读 + if !util.IsSubPath(util.WorkspaceDir, abs) || util.IsSensitivePath(abs) { + ret.Code = -1 + ret.Msg = fmt.Sprintf("asset path %s is outside the workspace or sensitive", abs) + return CallToolResult{}, fmt.Errorf("asset path outside workspace: %s", abs) + } fileList[i] = abs } succMap, err := model.InsertLocalAssets(id, fileList, true) ```

Source published

2 Oct 2026 23:16:56 UTC

Source modified

7 Oct 2026 17:56:03 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

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

Publisher rating · MODERATE

SiYuan MCP asset.upload Reads Arbitrary Absolute File Paths (Workspace Boundary Bypass) in github.com/siyuan-note/siyuan/kernel

Source published

7 Oct 2026 14:10:14 UTC

Source modified

7 Oct 2026 17:56:03 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

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

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.