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TI-2026-05842 Aliases CVE-2026-6657

CORS Origin Validation Bypass in jupyter-server

Priority HIGH 71CWE-346Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
High · High · High
Fix status
Deferred Red Hat: fix deferred

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-346.

Summary

A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the `allow_origin_pat` configuration is used. The issue arises from the use of `re.match()` for validating the `Origin` header, which only anchors at the start of the string. This allows attacker-controlled domains such as `trusted.example.com.evil.com` to pass validation against patterns intended to match `trusted.example.com`. The vulnerability affects multiple locations in the codebase, including CORS headers, WebSocket connections, referer validation, and login redirects, potentially enabling phishing attacks, arbitrary code execution, and unauthorized access to sensitive API responses.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.05213 92nd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Deferred Red Hat: fix deferred

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
jupyterlabjupyter/jupyterup to latest—No fix listedCNA
  • jupyter/jupyter Vendorjupyterlab Affected up to latest Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:jupyter:jupyter_server:*:*:*:*:*:*:*:*1.12.0 – 2.17.0Vulnerablejupyterlab
  • cpe:2.3:a:jupyter:jupyter_server:*:*:*:*:*:*:*:* Versions 1.12.0 – 2.17.0 Vulnerable ·jupyterlab

Remediation

No fixed version listed by the sources yet.

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Migration Toolkit for Applications 8AffectedNo fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)AffectedNo fix yet: Fix deferred

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-6657
  2. 2026-10-25 EPSS moved to the 90th–95th percentile

References

Exploit 1

  • TI-2026-04748 Path Traversal in jupyter/jupyter CVSS 3.1HIGH 8.1
  • TI-2026-27533 jupyter-server path traversal allows access to sibling directories sharing root_dir name prefix CVSS 4.0HIGH 7.6
  • TI-2025-38102 jupyter_server next parameter open redirect can redirect users to external domains CVSS 4.0MEDIUM 6.3
  • TI-2026-32614 Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP CVSS 4.0CRITICAL 9.3
  • TI-2024-23252 Jupyter server on Windows discloses Windows user password hash CVSS 3.1HIGH 7.5
  • TI-2022-11782 Known or guessable hidden files may be accessed in Jupyter Server CVSS 3.1HIGH 8.8
See all 14 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences