Overview
CVE-2026-6977 describes a Broken Function Level Authorization issue in a Vanna AI component that used a Legacy Flask API up to version 2.0.2. The vulnerability stems from an implicit trust relationship where an internal function could be invoked through a generic dispatch mechanism without enforcing per-function access controls. Attackers could remotely trigger the flaw to access or modify resources that should be restricted to privileged roles. This aligns with CWE-266 (Incorrect Principal/Identity) and CWE-285 (Improper Authorization). In Flask-based code, such flaws commonly occur when a route uses a dynamic function map or reflective invocation to handle actions, bypassing explicit role checks for each operation. The real-world impact is elevated access to sensitive user data or admin actions without proper authentication or authorization barriers, and the vulnerability could be exploited by remote adversaries if the app is publicly reachable.
In practice, the vulnerability manifests when a Flask app exposes an endpoint that dispatches user-supplied actions to internal functions without validating that the caller has the right permission for the chosen action. For example, a route may map an action name to a function and invoke it directly after basic authentication. If the function-level authorization is not enforced, a user can request privileged actions (like updating another user’s data) simply by specifying the action name. Remediating this requires explicit per-action access checks, whitelisting of actions, and strong authentication/authorization guarantees at the HTTP boundary rather than relying on internal function guards alone. The CVE demonstrates the risks of mixing legacy Flask API usage with insufficient authorization checks in a dispatch pattern.
This guide provides concrete Flask code examples showing a vulnerable pattern and a secure fix, tied to CVE-2026-6977, and outlines practical steps to harden function-level authorization in modern Flask apps.
Affected Versions
Vanna AI vanna up to 2.0.2 (Legacy Flask API)
Code Fix Example
Flask API Security Remediation
from flask import Flask, request, jsonify
app = Flask(__name__)
# Simple, explicit current user extraction (replace with real auth, e.g., JWT)
def get_current_user():
username = request.headers.get("X-User", "guest")
role = request.headers.get("X-Role", "guest")
return {"username": username, "role": role}
# --- Functions that perform actions ---
def read_profile(target, payload=None):
# In a real app, fetch and return sensitive profile data
return {"target": target, "data": "sensitive_profile_data"}
def update_profile(target, payload):
# In a real app, apply updates to the target profile
return {"target": target, "updated": payload}
ALLOWED_ACTIONS = {
"read_profile": read_profile,
"update_profile": update_profile,
}
# Vulnerable pattern: dynamic dispatch without per-action authorization
@app.route("/vuln/execute", methods=["POST"])
def vuln_execute():
user = get_current_user()
data = request.json or {}
action = data.get("action")
target = data.get("target")
if action not in ALLOWED_ACTIONS:
return jsonify({"error": "invalid action"}), 400
func = ALLOWED_ACTIONS[action]
# No per-action authorization check; any authenticated user may call any action
return jsonify(func(target, data.get("payload")))
# Secure pattern: per-action authorization enforced explicitly
REQUIRED_ROLES = {
"read_profile": ["viewer", "admin"],
"update_profile": ["admin"],
}
def has_role(user, roles):
return user.get("role") in (roles or [])
@app.route("/fixed/execute", methods=["POST"])
def fixed_execute():
user = get_current_user()
data = request.json or {}
action = data.get("action")
target = data.get("target")
if action not in ALLOWED_ACTIONS:
return jsonify({"error": "invalid action"}), 400
required = REQUIRED_ROLES.get(action, [])
if not has_role(user, required):
return jsonify({"error": "forbidden"}), 403
func = ALLOWED_ACTIONS[action]
return jsonify(func(target, data.get("payload")))
if __name__ == "__main__":
app.run(debug=True)