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User.get_user() built a raw SQL string via f-string interpolation of
the username path param and executed it directly, allowing classic
UNION/boolean-based SQL injection (API8:2019 Injection).
Switch to a parameterized query using SQLAlchemy's text() bound
parameter (:username) so the value is always passed as data, never
concatenated into the SQL statement.
Verified locally: UNION/boolean injection payloads against
GET /users/v1/{username} (e.g. "name1' OR '1'='1", UNION SELECT
dumping the admin row, and a bare trailing quote) all now resolve as
'User not found' with no SQL error, while legitimate lookups for
name1, name2, and admin still return the correct user JSON.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
🏆 VAmPI — CTF Patch Score1 / 9 challenges patched
Commit: 🎉 Your result is on the leaderboard — see where you rank! 🏆 |
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Vulnerability
GET /users/v1/{username}built a raw SQL statement via f-string interpolation of theusernamepath parameter (models/user_model.py,User.get_user()) and executed it withdb.session.execute(text(user_query)), allowing classic UNION/boolean-based SQL injection.Fix
Use a parameterized query: build the SQL with a named bind placeholder (
:username) via SQLAlchemy'stext()and pass the untrusted value as a parameter dict, so it is always treated as data and never concatenated into the SQL string.Testing
Ran the app locally (
vulnerable=1) and confirmed:GET /users/v1/{username}(name1' OR '1'='1, a UNION SELECT attempting to dump the admin row, and a bare trailing single quote) all now return{"status": "fail", "message": "User not found"}with no SQL error / no data leak.name1,name2, andadminall return their correct{"username":..., "email":...}JSON.🤖 Generated with Claude Code