knowns before 0.30.0 Path Traversal via MCP doc and memory tools

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knowns versions before 0.30.0 fail to validate filesystem paths in MCP tool arguments, allowing attackers to read, create, overwrite and delete files outside the project directory. Attackers can supply path arguments containing directory traversal sequences to access arbitrary Markdown files accessible to the server process.

Source published

7 Sep 2026 23:03:16 UTC

Source modified

24 Sep 2026 14:21:21 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS 3.1 · 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

knowns versions before 0.30.0 fail to validate filesystem paths in MCP tool arguments, allowing attackers to read, create, overwrite and delete files outside the project directory. Attackers can supply path arguments containing directory traversal sequences to access arbitrary Markdown files accessible to the server process.

Source published

Sep 7, 2026, 11:03:16 PM (timezone not stated)

Source modified

Sep 24, 2026, 2:21:21 PM (timezone not stated)

Saved here

11 Nov 2026 17:02:38 UTC

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ENISA EUVD · source terms and attribution apply

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EUVD CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

knowns versions before 0.30.0 fail to validate filesystem paths in MCP tool arguments, allowing attackers to read, create, overwrite and delete files outside the project directory. Attackers can supply path arguments containing directory traversal sequences to access arbitrary Markdown files accessible to the server process.

Source published

7 Sep 2026 23:16:53 UTC

Source modified

8 Sep 2026 19:56:50 UTC

Saved here

25 Oct 2026 16:19:16 UTC

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NIST NVD usage terms; underlying source attribution retained

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CVSS 4.0 · [email protected] · Secondary · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/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 · 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

## Overview Verified. Multiple **Unrestricted Path Traversal** vulnerabilities exist in the Knowns MCP `docs` and `memory` tools, allowing arbitrary file read, write, and deletion operations outside the project sandbox. The storage layer functions (`Get`, `Create`, `Update`, `Rename`, `Delete`) in both `doc_store.go` and `memory_store.go` concatenate user-controlled paths with `filepath.Join()` without any containment validation. Additionally, the `docs.update` action with a `newPath` parameter performs a file deletion via `Rename()`, but is classified as `CapWrite` in the permission registry rather than `CapDelete`. This allows an attacker with a `read-write-no-delete` preset to bypass deletion restrictions and destroy arbitrary files outside the project root. ## Affected paths | File Path | Role | Vulnerability & Execution Impact | | :--- | :--- | :--- | | **`internal/storage/doc_store.go`** | Vulnerable Sink (Docs) | **Path Traversal in File Operations (CWE-22):** `Get()`, `Create()`, `Update()`, `Rename()`, `Delete()` join user-controlled `path` with `filepath.Join(ds.docsDir(), ...)` without validating path containment. | | **`internal/storage/memory_store.go`** | Vulnerable Sink (Memory) | **Path Traversal in Memory Operations (CWE-22):** `GetInLayer()`, `Create()`, `Update()`, `Delete()` join user-controlled `id` with `filepath.Join(dir, models.MemoryFileName(id))` without validation. | | **`internal/mcp/handlers/doc.go`** | Pass-Through Handler | **Unsanitized Input Propagation:** MCP handlers pass user-supplied `path`, `folder`, `newPath` directly to storage layer without sanitization. | | **`internal/mcp/handlers/memory.go`** | Pass-Through Handler | **Unsanitized Input Propagation:** MCP handlers pass user-supplied `id` directly to storage layer without sanitization. | | **`internal/permissions/registry.go`** | Authorization Bypass | **Capability Misclassification (CWE-863):** `docs.update` with `newPath` performs file deletion but is classified as `CapWrite`, bypassing `CapDelete` restrictions. | ## Root Cause ### Missing Path Containment in DocStore In `internal/storage/doc_store.go`, all file operations use `filepath.Join()` to construct absolute paths without validating that the resolved path remains within `docsDir()`: ```go // Get retrieves a doc by its relative path (without .md extension). func (ds *DocStore) Get(path string) (*models.Doc, error) { path = strings.TrimPrefix(path, "/") path = strings.TrimSuffix(path, ".md") // VULNERABLE: No containment check absPath := filepath.Join(ds.docsDir(), filepath.FromSlash(path)+".md") if _, err := os.Stat(absPath); err == nil { // ... return ds.parseFile(absPath, path, folder, false, "") } // ... } // Create writes a new doc to .knowns/docs/{path}.md. func (ds *DocStore) Create(doc *models.Doc) error { if doc.Path == "" { return fmt.Errorf("doc path is required") } // VULNERABLE: No containment check absPath := filepath.Join(ds.docsDir(), filepath.FromSlash(doc.Path)+".md") if err := os.MkdirAll(filepath.Dir(absPath), 0755); err != nil { return fmt.Errorf("create doc dir: %w", err) } return ds.writeFile(absPath, doc) } // Rename rewrites a doc to a new path and removes the old file. func (ds *DocStore) Rename(oldPath string, doc *models.Doc) error { // ... oldAbsPath := filepath.Join(ds.docsDir(), filepath.FromSlash(strings.TrimSuffix(oldPath, ".md"))+".md") newAbsPath := filepath.Join(ds.docsDir(), filepath.FromSlash(strings.TrimSuffix(doc.Path, ".md"))+".md") // ... if err := ds.writeFile(newAbsPath, doc); err != nil { return err } if oldAbsPath != newAbsPath { // VULNERABLE: Deletes file at oldAbsPath (can be outside docsDir) if err := os.Remove(oldAbsPath); err != nil && !os.IsNotExist(err) { return err } } return nil } // Delete removes a doc file. func (ds *DocStore) Delete(path string) error { path = strings.TrimSuffix(path, ".md") // VULNERABLE: No containment check absPath := filepath.Join(ds.docsDir(), filepath.FromSlash(path)+".md") return os.Remove(absPath) } ``` **Critical Flaws:** - `filepath.Join` resolves `../` sequences natively - No post-Join prefix check (e.g., `strings.HasPrefix(absPath, ds.docsDir())`) - No rejection of absolute paths or path traversal sequences - `Rename()` performs file deletion via `os.Remove(oldAbsPath)`, which can target files outside the docs directory ### Missing Path Containment in MemoryStore In `internal/storage/memory_store.go`, memory operations similarly lack path validation: ```go // GetInLayer retrieves a memory entry by ID from a specific layer only. func (ms *MemoryStore) GetInLayer(id, layer string) (*models.MemoryEntry, error) { // ... dir, err := ms.dirForLayer(layer) if err != nil { return nil, err } // VULNERABLE: No containment check for id containing "../" absPath := filepath.Join(dir, models.MemoryFileName(id)) if _, err := os.Stat(absPath); err != nil { return nil, fmt.Errorf("memory %q not found in %s layer", id, layer) } return ms.parseFile(absPath, layer) } // Create writes a new memory entry to the appropriate layer directory. func (ms *MemoryStore) Create(entry *models.MemoryEntry) error { // ... dir, err := ms.dirForLayer(entry.Layer) if err != nil { return err } if err := os.MkdirAll(dir, 0755); err != nil { return fmt.Errorf("create memory dir: %w", err) } // VULNERABLE: No containment check for entry.ID containing "../" absPath := filepath.Join(dir, models.MemoryFileName(entry.ID)) return atomicWrite(absPath, []byte(renderMemory(entry))) } // Delete removes a memory entry by ID. func (ms *MemoryStore) Delete(id string) error { // ... filename := models.MemoryFileName(id) dirs := []string{ms.projectDir(), ms.globalDir()} for _, dir := range dirs { // VULNERABLE: No containment check absPath := filepath.Join(dir, filename) if _, err := os.Stat(absPath); err == nil { return os.Remove(absPath) } } return fmt.Errorf("memory %q not found", id) } ``` ### Authorization Bypass via Rename-as-Delete In `internal/mcp/handlers/doc.go`, the `handleDocUpdate()` function accepts a `newPath` parameter that triggers a rename operation: ```go func handleDocUpdate(getStore func() *storage.Store, req mcp.CallToolRequest) (*mcp.CallToolResult, error) { // ... if v, ok := stringArg(args, "newPath"); ok && strings.TrimSpace(v) != "" { doc.Path = strings.Trim(strings.TrimSuffix(v, ".md"), "/") } // ... if oldPath != doc.Path { if err := store.Docs.Rename(oldPath, doc); err != nil { return errFailed("rename doc", err) } // ... } // ... } ``` The `Rename()` function in `doc_store.go` performs file deletion: ```go if oldAbsPath != newAbsPath { if err := os.Remove(oldAbsPath); err != nil && !os.IsNotExist(err) { return err } } ``` However, in `internal/permissions/registry.go`, `docs.update` is classified as `CapWrite`: ```go "docs.update": {Capability: CapWrite, Target: TargetDoc, Risk: RiskMedium}, ``` This allows an attacker with a `read-write-no-delete` preset (which permits `CapWrite` but denies `CapDelete`) to delete files by using `docs.update` with a `newPath` parameter. ## Attack Vector | Phase | Request / Action | Effect | | :--- | :--- | :--- | | **1. Arbitrary File Read** | `docs.get` with `path="../../../victim/secret"` | Server reads file outside project root via path traversal in `DocStore.Get()`. | | **2. Arbitrary File Write** | `docs.create` with `folder="../../../victim"` | Server writes file outside project root via path traversal in `DocStore.Create()`. | | **3. Arbitrary File Delete** | `docs.update` with `path="../outside/secret.md"` and `newPath="../../../victim/renamed.md"` | Server deletes file outside project root via path traversal in `DocStore.Rename()`. Bypasses `CapDelete` restriction because `docs.update` is classified as `CapWrite`. | | **4. Memory File Read/Write** | `memory.update` with `id="x/../../../../victim/secret"` | Server reads and overwrites file outside project root via path traversal in `MemoryStore.Update()`. | ## Analysis ### Classic Path Traversal Pattern Both `DocStore` and `MemoryStore` follow the same vulnerable pattern: user-controlled input is concatenated with a base directory using `filepath.Join()`, then passed directly to file system operations (`os.ReadFile`, `os.WriteFile`, `os.Remove`, `os.Stat`) without any validation. ```go absPath := filepath.Join(baseDir, filepath.FromSlash(userInput)) // No containment check: strings.HasPrefix(absPath, baseDir) // No rejection of ".." or absolute paths ``` `filepath.Join` resolves `../` sequences, allowing attackers to escape the intended directory: - Input: `"../../../etc/passwd"` - Result: `/project/.knowns/docs/../../../etc/passwd` → `/etc/passwd` ### Rename-as-Delete Authorization Bypass The `Rename()` function performs two operations: 1. Write the file to the new location (`newAbsPath`) 2. Delete the file from the old location (`oldAbsPath`) Both paths are vulnerable to traversal. An attacker can: - Set `path` to a file outside the project (e.g., `"../../../victim/target.md"`) - Set `newPath` to another location outside the project - The `Rename()` function will delete the file at `path` (outside the project) Because `docs.update` is classified as `CapWrite` rather than `CapDelete`, this operation bypasses deletion restrictions in `read-write-no-delete` presets. ### Compounding Factor - Unauthenticated Access Due to the previously identified **Auth Bypass** vulnerability, all MCP tools are accessible without credentials when the server is started without a password, making this a zero-credential attack. ## Fix *Patch is available right now at [New Release](https://github.com/knowns-dev/knowns/releases).*

Source published

25 Sep 2026 19:32:05 UTC

Source modified

25 Sep 2026 19:45:09 UTC

Saved here

24 Oct 2026 13:17:17 UTC

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GitHub Advisory Database · CC-BY-4.0

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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:L/UI:N/S:U/C:H/I:H/A:H

Publisher rating · HIGH

## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-9gfj-28hw-jchp. This link is maintained to preserve external references. ## Original Advisory knowns versions before 0.30.0 fail to validate filesystem paths in MCP tool arguments, allowing attackers to read, create, overwrite and delete files outside the project directory. Attackers can supply path arguments containing directory traversal sequences to access arbitrary Markdown files accessible to the server process.

Source published

8 Sep 2026 00:30:22 UTC

Source modified

25 Sep 2026 17:30:06 UTC

Saved here

24 Oct 2026 13:17:17 UTC

Source terms

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:L/UI:N/S:U/C:H/I:H/A:H

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/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 · HIGH