CVE-2026-6657: jupyter/jupyter · Origin Validation Error
Affects jupyter/jupyterSource CVE Database V5
Not known to be exploited · CVSS 6.1 Medium.
Data as of 26 Oct 2026, 17:16 UTC
- 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:NExploitation evidence
Disclosed: evidence found.
CVE published 3 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| jupyterjupyter/jupyter | Affected
| 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.