Security readout for executives and security teams
Plain-English summary
JupyterLab’s extension installation policy could be bypassed through its API, allowing a permitted user to install an extension that the configured allow-list should have blocked. A malicious extension could compromise sensitive notebooks, data, credentials, or service availability. JupyterLab 4.5.7 fixes the issue.
Executive priority
Treat this as a high-priority patching issue for shared, remotely reachable, or sensitive research environments. Accelerate remediation where JupyterLab holds valuable datasets, credentials, models, or production access. With no supplied evidence of active exploitation, emergency incident response is not automatically warranted, but unexpected extensions should trigger investigation.
Technical view
JupyterLab 4.0.0 through 4.5.6 did not correctly enforce allowed_extensions_uris in the PyPI Extension Manager API. The GUI policy could therefore differ from POST-request behavior, and package selection was not confined as intended. CVSS 3.1 rates this 8.8: network-accessible, low complexity, low privileges, no user interaction, with high confidentiality, integrity, and availability impacts.
Likely exposure
Exposure is most likely where JupyterLab 4.0.0–4.5.6 enables the PyPI Extension Manager and relies on allowed_extensions_uris to restrict installations. Risk increases when lower-privileged or otherwise untrusted users can access JupyterLab and its Extension Manager API. The bundle does not establish whether the vulnerable feature is enabled by default in every deployment.
Exploitation context
CISA KEV status is false, and the supplied sources provide no evidence of active exploitation. Exploitation requires low privileges according to the CVSS vector but does not require user interaction. The primary concern is installation of a malicious third-party extension despite an administrator’s allow-list policy.
Researcher notes
The core weakness is server-side policy enforcement failure: an API request could bypass restrictions represented in the GUI. CWE-602 and CWE-88 are assigned in the source bundle. Validate both extension-manager configuration and API enforcement after upgrading. The supplied evidence does not establish public exploit availability, observed attacks, or universal default exposure.
Mitigation direction
- Upgrade JupyterLab to version 4.5.7 or later.
- Prioritize internet-accessible or multi-user deployments where untrusted users can access JupyterLab.
- Review JupyterLab’s vendor advisory for any deployment-specific guidance.
- Apply applicable Red Hat errata when using affected Red Hat-packaged software.
- Restrict Extension Manager access to trusted users until remediation is verified.
Validation and detection
- Inventory JupyterLab versions and identify installations running 4.0.0 through 4.5.6.
- Confirm whether the PyPI Extension Manager and allowed_extensions_uris are configured.
- Review installed extensions for unexpected, unapproved, or recently added packages.
- Verify remediated systems report JupyterLab 4.5.7 or later.
- Confirm the API now rejects extensions excluded by the configured policy.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-602: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-88: Command execution behavior lookup
Command injection weaknesses can lead defenders to review execution techniques and command interpreter telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-42266 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9GitHub_MCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9redhat-SADPVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- ADP timelineredhat-SADP
Made public.
- CVE publishedCVE Program
The CVE record was published.
- ADP timelineredhat-SADP
Reported to Red Hat.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-05-13T16:02:13.807Z: Reported to Red Hat.
- 2026-05-13T15:08:49.846Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4CVE reference, GitHub_M · x_refsource_CONFIRM
- https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7CVE reference, GitHub_M · x_refsource_MISC
- https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.htmlCVE reference, GitHub_M · x_refsource_MISC
- https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementationsCVE reference, GitHub_M · x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-42266CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2477072CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42266.jsonCVE reference, redhat-SADP · x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:43038CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:60520CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Client-Side Enforcement of Server-Side Security
Client-Side Enforcement of Server-Side Security represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
Improper Neutralization of Argument Delimiters in a Command ('Argument Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.