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CVE-2026-44727

Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP

CVSS score

9.3

EPSS probability

%0.4

Risk score

0.0

Published

3 mo ago

OverviewPublic Exploits (0)NewsroomVulnerability Timeline
Official patch verified

Etkilenen ürün ve sürüm için yayımlanan güvenlik güncellemesini uygulayın.

Impact on My Inventory

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Vulnerability description

DayBreach CVE AI Research

CVE-2026-44727 has vendor, distribution, patch and security-source records on file. We can compare them and prepare an explanation linked to the evidence.

Jupyter Server is the backend for Jupyter web applications. Prior to 2.20, the nbconvert HTTP handlers in jupyter_server render user-authored notebook HTML under the Jupyter origin without a sandbox directive in their Content-Security-Policy. Combined with nbconvert.HTMLExporter's default non-sanitizing behavior, a notebook carrying an HTML payload in a display_data output triggers stored XSS with cookie access, full /api/* authority, and kernel RCE. This vulnerability is fixed in 2.20.

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2026-44727 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

IDVENDORPRODUCTACTION
1jupyter-serverjupyter_server View
2jupyterjupyter server View
3pypijupyter-server View
4pypijupyter-server View
Total affected vendors: 3|Products: 4

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCOREVERSIONSEVERITYVECTORSOURCE
9.3CVSS V40CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XNVD
9.3CVSS 4.0—Vector not publishedGitHub Advisory
9.3CVSS V4_0CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:HCVE CNA
9.0CVSS V31CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:HNVD
9.0CVSS V3_1CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:HCVE ADP
5.4CVSS V31MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:NNVD
5.4CVSS 3.x—Vector not publishedGitHub Advisory

Patch and Remediation Guide

Solution & Remediation Advisory

Patch verified

3 doğrulanmış yama veya düzeltilmiş sürüm kanıtı bulundu.

nvd

NVD tarafından Patch olarak etiketlenmiş referans

Open source
nvd

NVD tarafından Patch olarak etiketlenmiş referans

Open source
osvjupyter-server2.20.0

OSV düzeltilmiş sürüm: 2.20.0

Confirm the affected product and version against the source evidence above.
Restrict access to internet-facing services and apply network segmentation.
Apply the official update named in the evidence only to the matching product and version.
Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-44727 is associated with the following CWEs:

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')CWE-1021: Common Weakness Enumeration Entry CWE-1021

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-44727 weaknesses.

CAPEC-66: SQL InjectionCAPEC-126: Path TraversalCAPEC-28: OS Command Injection

Attack Vector and Accessibility

ExposureAğ üzerinden
PermissionsLow
User—

Official Sources and Advisories

https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmpvendor-advisoryhttps://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bdvendor-advisoryhttps://access.redhat.com/errata/RHSA-2026:43038nvdhttps://access.redhat.com/errata/RHSA-2026:60520nvdhttps://access.redhat.com/security/cve/CVE-2026-44727nvdhttps://bugzilla.redhat.com/show_bug.cgi?id=2491516nvdhttps://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44727.jsonnvdhttps://nvd.nist.gov/vuln/detail/CVE-2026-44727vendor-advisoryhttps://github.com/advisories/GHSA-fcw5-x6j4-ccmpvendor-advisoryhttps://github.com/jupyter-server/jupyter_servervendor-advisory

CVSS Vector Radar Chart

9.3 / 10
Attack VectorNetworkComplexityLowPrivilegesLowUser Interact.RequiredConfidentialityLowIntegrityNoneAvailabilityHigh

Vulnerability Scoring Details

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredLow privileges
User InteractionA
Confidentiality (Gizlilik)Low
Integrity (Bütünlük)A
Availability (Erişilebilirlik)High

Yama doğrulandı

3 doğrulanmış yama veya düzeltilmiş sürüm kanıtı bulundu.

Follow the vendor

J
jupyter-server logo
jupyter-server
J
jupyter logo
jupyter
P
pypi logo
pypi

Weakness Type (CWE & CAPEC)

CWE-79 CWE-1021

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