Critical· 9.3official fix available
CVE-2026-44727
A security flaw in Jupyter Server allows attackers to inject malicious code into notebooks. When a user views a notebook containing this code, the malicious script runs within the user's browser session.
publishedJun 22, 2026
last modifiedJul 22, 2026
sourcesNVD
severity · cvss
9.3
critical · how bad it is
exploitation · epss
<1%
23th percentile · chance of exploitation in 30 days
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →
auto-deletes from the system
counting…on Aug 22, 2026
An official fix is available, so this entry is kept for 30 days and then removed automatically.
01
Who is affected
Users of Jupyter Server versions prior to 2.20.
02
Real-world impact
An attacker could steal sensitive cookies, gain full control over the Jupyter API, and execute arbitrary commands on the server via the notebook kernel.
03
Why this severity
The critical score reflects that an attacker can achieve full remote code execution and complete control over the server by exploiting a vulnerability that requires minimal user interaction.
04
What to do about it
official fix available
recommended steps
- 01Upgrade Jupyter Server to version 2.20 or later.
NVD-referenced vendor advisory
05
Timeline
- Jun 22, 2026 · Jun 22, 2026PublishedDisclosed and added to the National Vulnerability Database.
- Jul 22, 2026 · 13d agoAdvisory updatedThe NVD record was last revised.
- Jul 23, 2026 · 12d agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.
06
How it’s attacked
Attack vectorNetwork (remote)
Attack complexityLow
Attack requirementsNone
Privileges requiredLow
User interactionActive
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
07
References & advisories
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →