CVE-2026-67338 JupyterLab before 4.5.9 Stored XSS via Extension Manager
Attackers can execute arbitrary JavaScript in JupyterLab via malicious PyPI packages with javascript: URLs in metadata, potentially leading to account takeover.
- 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-2026-67338?
CVE-2026-67338 is a medium-severity cross-site scripting vulnerability in jupyterlab, published on 1 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
JupyterLab before 4.5.9 contains a stored cross-site scripting vulnerability in the Extension Manager that fails to validate URI protocols in package metadata URLs. Attackers can publish malicious PyPI packages with javascript: URLs in project metadata that execute arbitrary JavaScript in the JupyterLab origin when users click the extension name.
Weakness: CWE-84
Which versions are affected by CVE-2026-67338?
3 open source packages ship an affected version, including jupyterlab.
| Package | Affected | Fixed in |
|---|---|---|
jupyterlab Bitnami | All versions | 4.5.9 |
jupyterlab PyPI | All versions | 4.5.9 |
jupyterlab PyPI | All versions | 4.5.9 |
How do I fix CVE-2026-67338?
Upgrade jupyterlab to 4.5.9 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-67338 being exploited?
There is no known exploitation of CVE-2026-67338 in the wild and no public exploit code.
Sources
Also known as BIT-jupyterlab-2026-67338, CLEANSTART-2026-HX81668, DEBIAN-CVE-2026-67338, GHSA-r75g-r7w6-363h, GHSA-vmhf-c436-hxj4, UBUNTU-CVE-2026-67338.