Frappe LMS is a popular open source learning management system (LMS) for setting up online courses, managing users, and tracking learning progress. It’s widely adopted due to its flexibility and free availability. But on October 10, 2023, a security flaw—CVE-2023-42807—was disclosed, impacting all versions up to and including 1... This long-read aims to explain how the vulnerability worked, how it can be exploited, and how you can prevent it in your Frappe LMS setup.
What is CVE-2023-42807?
CVE-2023-42807 is a SQL Injection vulnerability in the “People” Page of Frappe LMS. This means attackers could send specially crafted input to the application, which would then be interpreted as SQL commands, potentially allowing them to access or mess with the database backend.
If you’re running Frappe LMS 1.. or earlier and have not updated to the main branch, you are at risk!
Official references
- Github Security Advisory
- CVE Record at NVD
Take control of the application if the DB user has high privileges.
Attackers might use simple tricks in URLs or form data to inject their own queries and bypass security.
Where’s the Problem? (Technical Analysis)
In Frappe LMS (1.. and earlier), the People page handled filtering and search through user-provided input without cleaning it properly before building SQL queries. That allowed attackers to slip in malicious SQL.
A simplified code snippet (based on this diff):
# Vulnerable code:
filters = request.args.get("filters") # User input
sql = f"SELECT * FROM tabUser WHERE {filters}"
users = frappe.db.sql(sql, as_dict=True)
If filters is not thoroughly checked, an attacker can set it to something like 1=1; DROP TABLE tabUser—and that could wipe out all user records.
How to Exploit CVE-2023-42807 (Demonstration)
Let’s say you have access to the People page, and the app takes a filters GET parameter as input.
Example request
GET /api/people?filters=1=1;--+
Behind the scenes, this ends up as
SELECT * FROM tabUser WHERE 1=1;--+
Which exposes all users (that’s just a basic info leak). But if the attacker tries
GET /api/people?filters=1=1; DROP TABLE tabUser;--+
That could lead to permanent data loss!
For a real-world attack, an attacker could use automated tools like sqlmap to find the parameter and dump your entire database.
Has This Been Fixed? How?
Yes, it’s fixed!
The Frappe LMS team patched the vulnerability quickly. The main fix (commit link) ensures user inputs are properly sanitized and variables are passed to SQL through parameterized queries, not string formatting.
Patched code sample
filters = sanitize_filters(request.args.get("filters")) # Clean input
sql = "SELECT * FROM tabUser WHERE some_field = %(filter)s"
users = frappe.db.sql(sql, {'filter': filters}, as_dict=True)
By using parameterized queries, attackers can’t inject their own SQL any more.
What Should You Do? (Mitigation)
- Upgrade immediately: Switch to the latest version on the main branch of Frappe LMS. The issue is fully fixed there.
- If you forked or customized, manually patch your code to use parameterized SQL everywhere you interact with the database.
> Not affected if you are already on the latest main branch!
Audit your code:
Make sure no SQL queries use string formatting (f"..." or %), only use framework-provided parameterization.
Follow upstream releases:
Keep up with the official Frappe LMS GitHub for new patches and security releases.
Further Reading
- SQL Injection Explained - OWASP
- Frappe LMS Security Advisories
In Summary
CVE-2023-42807 in Frappe LMS was a serious SQL injection bug affecting any site with version 1.. or earlier. Exploiting it could let hackers read or destroy your data. But the fix is simple: upgrade to the latest main branch and always sanitize user inputs. Don’t let your learning platform become a lesson for attackers.
Stay safe and up-to-date! If you have questions, check out the official repo or share in the comments below.
Timeline
Published on: 09/21/2023 17:15:23 UTC
Last modified on: 09/25/2023 16:34:41 UTC