jupyterlab: Improper Neutralization of Argument Delimiters in a Command
CVE-2026-42266 is a high-severity improper neutralization of argument delimiters in a command vulnerability in jupyterlab, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected jupyterlab versions: >= 4.0.0, < 4.5.7. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 5.65% chance of exploitation within 30 days, which is in the top 6.91% of all scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of jupyterlab you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Jupyterlab | jupyterlab | >= 4.0.0, < 4.5.7 | Not stated |
| Red Hat | Red Hat Migration Toolkit for Applications 8.2 | Not specified in the record | Not stated |
| Red Hat | Red Hat OpenShift AI 3.4 | Not specified in the record | Not stated |
| Red Hat | Red Hat OpenShift AI (RHOAI) | Not specified in the record | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (github.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | CNA (github.com) |
| CVSS 3.1 | 8.8 | High | CNA |
Official description
JupyterLab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. From 4.0.0 to 4.5.6, the allow-list of extensions that can be installed from PyPI Extension Manager (allowed_extensions_uris) is not correctly enforced by JupyterLab. The PyPI Extension Manager was not contained to packages listed on the default PyPI index. This vulnerability is fixed in 4.5.7.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Argument Delimiters in a Command
The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.
How developers prevent this class of flaw
- Understand all the potential areas where untrusted inputs can enter your product: parameters or arguments, cookies, anything read from the network, environment variables, request headers as well as content, URL components, e-mail, files, databases, and any external systems that provide data to the application. Perform input validation at well-defined interfaces.
- Directly convert your input type into the expected data type, such as using a conversion function that translates a string into a number. After converting to the expected data type, ensure that the input's values fall within the expected range of allowable values and that multi-field consistencies are maintained.
- When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.
More Improper Neutralization of Argument Delimiters in a Command vulnerabilities (CWE-88)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
- github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7Release Notes
Other references
- jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.htmlProduct
- jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementationsProduct
- access.redhat.com/errata/RHSA-2026:43038
- access.redhat.com/errata/RHSA-2026:60520
- access.redhat.com/security/cve/CVE-2026-42266
- bugzilla.redhat.com/show_bug.cgi?id=2477072
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42266.json
Other vulnerabilities in jupyterlab
- 8.1 High severity
- 8.6 High severity
- 7.5 High severity
- 7.5 High severity
- 9.6 Critical severity
- 8.4 High severity
Recent Improper Neutralization of Argument Delimiters in a Command vulnerabilities
- 9.1 Critical severity
- 9.1 Critical severity
- 8.8 High severity
- 8.2 High severity
- 9.8 Critical severity
- 7.8 High severity
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