CVE-2025-23205 `frame-ancestors: self` grants all users access to formgrader in nbgrader
Attackers can steal grading data from authorized users by exploiting frame-ancestors settings in nbgrader when subdomains are disabled.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2025-23205?
CVE-2025-23205 is a medium-severity vulnerability in jupyter nbgrader, published on 17 Jan 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
nbgrader is a system for assigning and grading notebooks. Enabling frame-ancestors: 'self' grants any JupyterHub user the ability to extract formgrader content by sending malicious links to users with access to formgrader, at least when using the default JupyterHub configuration of `enable_subdomains = False`. #1915 disables a protection which would allow user Alice to craft a page embedding formgrader in an IFrame. If Bob visits that page, his credentials will be sent and the formgrader page loaded. Because Alice's page is on the same Origin as the formgrader iframe, Javasript on Alice's page has _full access_ to the contents of the page served by formgrader using Bob's credentials. This issue has been addressed in release 0.9.5 and all users are advised to upgrade. Users unable to upgrade may disable `frame-ancestors: self`, or enable per-user and per-service subdomains with `JupyterHub.enable_subdomains = True` (then even if embedding in an IFrame is allowed, the host page does not have access to the contents of the frame).
Weakness: CWE-668
Which versions are affected by CVE-2025-23205?
3 open source packages ship an affected version, including nbgrader.
| Package | Affected | Fixed in |
|---|---|---|
nbgrader PyPI | From 0.9.4 | 0.9.5 |
nbgrader PyPI | From 0.9.4 | 0.9.5 |
nbgrader PyPI | From 0.9.4 | 0.9.5 |
How do I fix CVE-2025-23205?
Upgrade nbgrader to 0.9.5 or later.
Is CVE-2025-23205 being exploited?
There is no known exploitation of CVE-2025-23205 in the wild and no public exploit code.
Sources
Also known as GHSA-fcr8-4r9f-r66m, PYSEC-2026-1692.