CVE-2026-40110
Description
A flaw was found in Jupyter Server. The Origin header validation, which uses Python's re.match() function, does not correctly validate incoming origins against allowed patterns. This allows a remote attacker to bypass Cross-Origin Resource Sharing (CORS) restrictions by crafting a malicious domain that partially matches a trusted one. Consequently, the attacker can make unauthorized cross-origin requests to the Jupyter Server API from an untrusted site, potentially leading to sensitive information disclosure or other unauthorized actions.
Mitigation
Administrators should review and update the `allow_origin_pat` configuration in Jupyter Server to use a more precise regular expression. Ensure the pattern explicitly anchors to the end of the string (e.g., by adding `$` to the end of the regex) to prevent partial domain matches. After modifying the configuration, the Jupyter Server service must be restarted for the changes to take effect.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.1 | 7.3 | 7.1 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | Low | None |
| User Interaction | Required | Required | Required |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | High | High | High |
| Integrity Impact | Low | High | Low |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
Frequently Asked Questions
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