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VulnerabilityPublished

CVE-2026-6657: jupyter/jupyter · Origin Validation Error

Affects jupyter/jupyterSource CVE Database V5

0

Not known to be exploited · CVSS 6.1 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.0 base score
6.1Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
6.1% chance of exploitation in 30 days – higher than 93% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
jupyterjupyter/jupyterAffected
  • ≥ unspecified, ≤ latest
Fixed in–

AI-suggested

Until an official fix is released, users should avoid using the allow_origin_pat configuration or apply strict manual validation of allowed origins. Monitor official jupyter advisories for updates and patches addressing this issue.

Description

CVE-2026-6657 is a medium severity vulnerability in jupyter-server versions 1.12.0 through 2.17.0 that allows bypassing of CORS origin validation when the allow_origin_pat configuration is used. The issue stems from improper use of re.match() for Origin header validation, which only anchors at the start of the string, enabling attacker-controlled domains that mimic trusted domains to bypass checks. This affects multiple code locations including CORS headers, WebSocket connections, referer validation, and login redirects, potentially leading to phishing, unauthorized access, and arbitrary code execution.

References

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