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Vulnerabilities

Vulnerability · CVE-2026-6657

A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used.

Published Jun 3, 2026 · catalog updated Jul 21, 2026 · jupyter server

Check if you run it

No confirmed exploitation is on record for CVE-2026-6657. EPSS is 0.27%. Act only if a listed version of jupyter server is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.27%
Remediation
Not established
Affected products
cpe jupyter/jupyter server

A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used. The issue arises from the use of for validating the header, which only anchors at the start of the string. This allows attacker-controlled domains such as to pass validation against patterns intended to match . 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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe jupyter/jupyter serverversion unspecified

How to fix CVE-2026-6657

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-6657. EPSS is 0.27%. Act only if a listed version of jupyter server is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-346. EPSS 0.27%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Jun 3, 2026 · NIST NVD

    Detected

    A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used. The issue arises from the use of for validating the header, which only anchors at the start of the string. This allows attacker-controlled domains such as to pass validation against patterns intended to match . The vulnerability affects multiple locat

  2. Jul 21, 2026 · NIST NVD

    Updated

    A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used. The issue arises from the use of for validating the header, which only anchors at the start of the string. This allows attacker-controlled domains such as to pass validation against patterns intended to match . The vulnerability affects multiple locat

Sources

  • FIRST EPSSExploitation probabilityCVE-2026-6657

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-6657

    A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the configuration is used. The issue arises from the use of for validating the header, which only anchors at the star

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.