Security readout for executives and security teams
Plain-English summary
A malicious or compromised notebook can display a convincing button that runs JupyterLab commands when clicked. Those commands may execute code with the user’s Jupyter privileges, potentially exposing data, altering notebooks, or disrupting the environment. The victim must open the content and click, but no explicit code-run approval is required.
Executive priority
Treat as a high-priority update, especially where staff exchange notebooks or process externally supplied research and data. Although exploitation requires a click and active exploitation is not established, a successful event can compromise confidentiality, integrity, and availability within the user’s Jupyter environment. Accelerate remediation for privileged or sensitive-data sessions.
Technical view
Before JupyterLab 4.5.7, sanitized HTML button output could retain command-linker attributes. JupyterLab’s CommandLinker processed body-wide clicks without verifying that the element belonged to trusted application UI. Consequently, pre-saved notebook output could invoke arbitrary JupyterLab commands, including commands enabling code execution. The issue is classified as CWE-79 and scored CVSS 3.1 8.8.
Likely exposure
Exposure includes JupyterLab versions below 4.5.7 and Jupyter Notebook versions 7.0.0 through 7.5.5. Risk is greatest where users open notebooks from external, shared, uploaded, or otherwise untrusted sources. Successful abuse requires a user click and operates within the permissions available to that Jupyter session.
Exploitation context
The supplied sources describe a one-click path from untrusted notebook HTML output to arbitrary JupyterLab command execution. User interaction is required, but the attacker needs no authenticated Jupyter privilege according to the CVSS vector. The bundle marks this CVE as absent from KEV and provides no evidence of active exploitation.
Researcher notes
The trust-boundary failure combines permissive HTML sanitization with global click delegation. Analysis should distinguish stored notebook output from user-submitted executable cells: the deceptive output is already present, and clicking it invokes a trusted command bridge. Assess downstream distributions and embedded JupyterLab deployments separately; the supplied bundle only identifies JupyterLab and Jupyter Notebook version ranges.
Mitigation direction
- Upgrade JupyterLab to version 4.5.7 or later.
- Upgrade Jupyter Notebook to version 7.5.6 or later.
- Prioritize shared, internet-accessible, research, and multi-user notebook environments.
- Until upgraded, avoid opening or interacting with notebooks from untrusted sources.
- Review applicable Red Hat advisories when using affected Red Hat packages.
Validation and detection
- Inventory deployed JupyterLab and Jupyter Notebook versions, including embedded and managed installations.
- Confirm JupyterLab is 4.5.7 or later.
- Confirm Jupyter Notebook is 7.5.6 or later.
- Verify dependency locks and built artifacts contain the remediated package versions.
- Run vendor regression tests confirming sanitized notebook output cannot activate command-linker commands.
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-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-42557 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:N/UI:R/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:N/UI:R/S:U/C:H/I:H/A:H2.85.9redhat-SADPCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——GitHub_MVulnerability scoring details
Base CVSS 4.0 score
8.6HighVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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
- 2026-05-13T16:02:57.063Z: Reported to Red Hat.
- 2026-05-13T15:06:14.222Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-mqcg-5x36-vfcgCVE reference, GitHub_M · x_refsource_CONFIRM
- https://access.redhat.com/security/cve/CVE-2026-42557CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2477086CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42557.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.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.