Security readout for executives and security teams
Plain-English summary
JupyterLab’s extension allow-list could be bypassed through the Extension Manager API. An authenticated user could install a third-party extension outside the intended PyPI restriction, potentially leading to code execution impact through malicious extensions. The issue affects JupyterLab 4.0.0 through 4.5.6 and is fixed in 4.5.7.
Executive priority
Treat as high priority for shared JupyterLab services. The attack requires an authenticated user, but the potential impact is broad because extensions can affect user environments and workloads. Patch promptly and review extension trust controls.
Technical view
The flaw is a policy enforcement discrepancy between the Extension Manager GUI/API and allowed_extensions_uris. Client-side or GUI expectations were not reliably enforced server-side for PyPI Extension Manager POST requests. CVSS 8.8 reflects network access, low complexity, required low privileges, no user interaction, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is most likely where JupyterLab 4.0.0 to 4.5.6 is deployed with the PyPI Extension Manager enabled, especially shared notebook, research, education, or internal analytics environments where users can authenticate and manage extensions.
Exploitation context
The bundle does not identify active exploitation, and KEV status is false. Exploitation requires authenticated low-privilege access but no user interaction. The main concern is abuse of extension installation policy to introduce malicious or unapproved packages.
Researcher notes
Focus validation on server-side enforcement of extension allow-list policy, not only GUI behavior. Evidence names CWE-602 and CWE-88, but the bundle provides limited implementation detail. Avoid assuming unauthenticated reachability or known exploitation without additional vendor confirmation.
Mitigation direction
- Upgrade affected JupyterLab installations to 4.5.7 or later.
- Inventory deployed JupyterLab versions and prioritize shared multi-user environments.
- Review and remove unexpected or untrusted JupyterLab extensions.
- Restrict Extension Manager access to trusted users until patched.
- Follow JupyterLab and platform vendor guidance for deployment-specific controls.
Validation and detection
- Confirm no JupyterLab instance runs version 4.0.0 through 4.5.6.
- Identify deployments using the PyPI Extension Manager and allowed_extensions_uris.
- Review extension installation history for unexpected packages.
- Check Red Hat advisories if consuming JupyterLab through Red Hat products.
- Verify patched systems report JupyterLab 4.5.7 or later.
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
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.