Format String in Django with Cockroachdb

A format string vulnerability occurs when user-controlled input is passed directly into string formatting functions without proper sanitization. In Django, this often arises in logging, error messages, or dynamic SQL construction. When using CockroachDB as the backend, the interaction between Django’s ORM and the database driver can expose risks if developer code bypasses the ORM and uses string formatting to build raw queries.

Consider a view that builds a SQL fragment using Python’s % operator or .format() with values derived from request parameters. For example:

table_or_column = request.GET.get('sort', 'id')
sql = 'SELECT id, name FROM my_table ORDER BY %s' % table_or_column
with connection.cursor() as cursor:
    cursor.execute(sql)

Even though CockroachDB is the database, the vulnerability is in the Python code, not the database itself. The database driver receives a string that may contain format specifiers like %s, %d, or even format verbs such as %x. If an attacker controls the input, they can cause information disclosure or application crashes. In a Django + CockroachDB setup, developers might mistakenly believe that using CockroachDB’s wire protocol or a specific driver removes risk, but the issue is at the application layer.

Django’s ORM normally protects against injection by using parameterized queries. However, when using cursor.execute(sql, params) correctly, placeholders are parameterized. The vulnerability appears when developers interpolate values directly into the SQL string before passing it to cursor.execute. CockroachDB does not sanitize format verbs; it treats them as part of the protocol or string if improperly handled by the client code.

Another scenario involves logging. Django’s logging configuration may include request details formatted with user data:

import logging
logger = logging.getLogger(__name__)
def my_view(request):
    user_input = request.GET.get('q', '')
    logger.info('User query: %s' % user_input)

If the log formatter uses a format string that includes the user input without proper escaping, and logs are later rendered in an admin interface or consumed by a tool that interprets format verbs, this can lead to log injection or potential execution in adjacent systems.

LLM/AI Security checks in middleBrick can detect unsafe consumption patterns where user input reaches execution contexts, including log formatting and raw query construction. The scanner identifies places where format verbs meet uncontrolled data, helping to prevent information leakage or instability in Django applications backed by CockroachDB.

Remediation centers on ensuring all database interactions use parameterized queries and that string formatting never interpolates untrusted data into executable structures.

Use Django ORM or parameterized raw queries

Always prefer the Django QuerySet API. If you must use raw SQL, use parameter substitution with a tuple or dictionary, never string interpolation:

# Safe: parameterized query with placeholders
with connection.cursor() as cursor:
    cursor.execute('SELECT id, name FROM my_table WHERE name = %s', [user_name])
    row = cursor.fetchone()

Avoid dynamic sorting or column names via string interpolation

Column and table names cannot be parameterized in SQL placeholders. If you must use dynamic identifiers, validate them against a strict allowlist:

allowed_columns = {'id', 'name', 'created_at'}
table_or_column = request.GET.get('sort', 'id')
if table_or_column not in allowed_columns:
    raise ValueError('Invalid column')
sql = 'SELECT id, name FROM my_table ORDER BY %s'
with connection.cursor() as cursor:
    cursor.execute(sql, [table_or_column])

Secure logging practices

Use logging formatter arguments instead of %-style interpolation to prevent format string injection in logs:

logger.info('User query: %s', user_input)

This ensures that user_input is treated as a log message argument, not as format syntax. middleBrick’s LLM/AI Security checks can flag unsafe logging patterns where format verbs are exposed to external input.

Validate and sanitize in middleware or forms

Apply strict validation early in the request lifecycle. For example, in a Django form or serializer, constrain acceptable values and reject unexpected input before it reaches database or logging code.

By combining Django’s built-in protections, careful use of parameterized queries, and allowlist validation for identifiers, you reduce the attack surface when using CockroachDB. middleBrick’s scans help verify that these practices are consistently applied across your API surface.