CVE-2026-84320: Nginx UI Path Traversal Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jrq7-xrjx-pcfw",
  "modified" : "2026-10-15T20:10:56Z",
  "published" : "2026-10-15T20:10:56Z",
  "aliases" : [ "CVE-2026-84320" ],
  "summary" : "Nginx UI: Auto backup name allows path traversal outside validated storage path",
  "details" : "## Summary\n\nNginx UI validates `backup_path` and `storage_path` against the administrator-defined `backup.GrantedAccessPath` boundary, but the final auto-backup output filename is built from the user-controlled auto-backup `name` without stripping path separators or `..` components.\n\nAn authenticated user who can create or modify an auto-backup task can set a name such as `task/../../../escaped`. The configured `storage_path` still passes validation because it is inside `GrantedAccessPath`, but the generated backup path escapes that storage directory when `filepath.Join(storage_path, filename)` resolves the embedded traversal sequence.\n\nThis bypasses the documented backup path boundary and allows backup archives, and for encrypted configuration backups the adjacent `.key` file, to be written outside the intended storage directory with the Nginx UI process privileges.\n\n## Affected Versions\n\n- Current `dev` branch commit checked: `4948fba8744e82c3d7003f68ee164e9f49421066`\n- Latest release checked: `v2.3.10`, published 2026-04-28\n- The vulnerable filename construction is present in both current `dev` and `v2.3.10`.\n\n## Security Boundary\n\nThe project documentation describes `backup.GrantedAccessPath` as the critical security boundary for backup operations. It says the setting:\n\n- restricts backup operations to explicitly authorized directories,\n- prevents unauthorized access to sensitive system directories,\n- enforces administrator-defined boundaries,\n- normalizes paths to prevent traversal attempts.\n\nThat boundary is enforced for the configured `storage_path`, but not for the final path after the backup name is appended.\n\n## Root Cause\n\n`model.AutoBackup.GetName()` only trims whitespace and replaces spaces:\n\n```go\nfunc (a *AutoBackup) GetName() string {\n    return strings.ReplaceAll(strings.TrimSpace(a.Name), \" \", \"_\")\n}\n```\n\nThe result is then embedded directly into filenames:\n\n```go\nfilename := fmt.Sprintf(\"%s_%d.zip\", autoBackup.GetName(), time.Now().Unix())\noutputPath = filepath.Join(autoBackup.StoragePath, filename)\n```\n\nand for custom directory backups:\n\n```go\nfilename := fmt.Sprintf(\"custom_dir_%s_%d.zip\", autoBackup.GetName(), time.Now().Unix())\noutputPath = filepath.Join(autoBackup.StoragePath, filename)\n```\n\nThe API validation rules require `name`, `backup_type`, `storage_type`, `storage_path`, and `cron_expression`, but do not reject `/`, `\\`, or `..` in `name`. `ValidateAutoBackupConfig` validates `backup_path` and `storage_path`, but it does not validate the final `outputPath` after appending the generated filename.\n\nRelevant paths:\n\n- `model/auto_backup.go`\n- `api/backup/auto_backup.go`\n- `internal/backup/auto_backup.go`\n- `internal/backup/utils.go`\n\n## Proof of Concept\n\nThe following local-only reproducer mirrors the relevant code path without contacting any external system:\n\n```go\nname := \"task/../../../escaped\"\nfilename := fmt.Sprintf(\"custom_dir_%s_%d.zip\", getName(name), int64(1715555555))\noutputPath := filepath.Join(storageDir, filename)\n```\n\nSetup:\n\n1. Create a temporary `granted` directory.\n2. Set `sourceDir` and `storageDir` under that granted directory.\n3. Treat only `granted` as the allowed path boundary.\n4. Use the auto-backup name `task/../../../escaped`.\n5. Create the custom-directory backup using the same filename pattern and zip creation behavior.\n\nObserved output:\n\n```text\ngranted_root=/Users/jagadeshachanta/.cache/tmp/nginx-ui-autobackup-poc-1538710430/granted\nvalidated_storage_path=/Users/jagadeshachanta/.cache/tmp/nginx-ui-autobackup-poc-1538710430/granted/storage\nauto_backup_name=\"task/../../../escaped\"\nconstructed_filename=\"custom_dir_task/../../../escaped_1715555555.zip\"\ncreated_file=/Users/jagadeshachanta/.cache/tmp/nginx-ui-autobackup-poc-1538710430/escaped_1715555555.zip\nescaped_validated_storage_path=true\ncreated_file_exists=true\n```\n\nThe configured storage path is inside the granted directory, but the created backup file is outside both the storage directory and the granted directory.\n\nA repo-local regression test was also prepared at:\n\n```text\ninternal/backup/auto_backup_path_traversal_poc_test.go\n```\n\nThe test cannot currently be executed cleanly in this checkout because unrelated build prerequisites fail before the package test runs:\n\n```text\napp/app.go: pattern all:dist: no matching files found\nmodel/cert.go: no required module provides package github.com/go-acme/lego/v5/certificate\ninternal/helper/key_type.go: no required module provides package github.com/go-acme/lego/v5/certcrypto\n```\n\nThe standalone reproducer output above was therefore used as the executable proof for this report.\n\n## Impact\n\nAn authenticated user with access to the auto-backup API can bypass the administrator-configured backup storage boundary. Depending on filesystem permissions and deployment layout, this can:\n\n- write backup archives outside the intended `storage_path`,\n- write encrypted configuration backup key files outside the intended `storage_path`,\n- place sensitive backup material in directories that administrators did not authorize for backup storage,\n- create or overwrite timestamp-suffixed files outside the validated backup directory using the Nginx UI process privileges.\n\nThis is especially relevant because backup archives may contain Nginx UI configuration, database files, Nginx configuration, and for encrypted config backups the adjacent key file required to decrypt the archive.\n\n## Suggested Fix\n\nRecommended defense in depth:\n\n1. Treat auto-backup `name` as a display label only, not as a filesystem path component.\n2. Sanitize generated filenames with `filepath.Base` or a strict allowlist such as `[A-Za-z0-9._-]`.\n3. Reject path separators, drive separators, NUL bytes, and `..` segments in `name`.\n4. After constructing `outputPath`, clean it and validate that the final path remains inside the already-validated `storage_path`.\n5. Add regression tests for both local and S3 temporary-file paths.\n\nExample invariant:\n\n```go\ncleanOutput := filepath.Clean(outputPath)\ncleanStorage := filepath.Clean(autoBackup.StoragePath) + string(filepath.Separator)\nif !strings.HasPrefix(cleanOutput, cleanStorage) {\n    return ErrPathNotInGrantedAccess\n}\n```\n\n## Disclosure Notes\n\nThis was tested only in a local isolated environment against source code and temporary directories. No online demo systems or production systems were tested.\n\nAI assistance was used to inspect the open-source code, prepare the local reproducer, and draft this report. The issue and PoC output were verified locally before submission.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/0xJacky/Nginx-UI"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.9.10-0.20260715121709-f92218e01054"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-jrq7-xrjx-pcfw"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-84320"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/commit/f92218e01054491fc1e6684dc6f7facaf8ab41eb"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/0xJacky/nginx-ui"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/releases/tag/v2.4.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-15T20:10:56Z",
    "nvd_published_at" : "2026-10-12T21:17:22Z"
  }
}