Vulnerability details
CVE-2026-44727
Red Hat OpenShift AIjupyter-server jupyter_server
Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP
CVSS 4.0
9.3Critical
Official description
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.
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 9.3Critical | 4.0 | CVEProject cvelistV5 (CNA) (GitHub_M) | 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 |
| 9.0Critical | 3.1 | CVEProject cvelistV5 (CNA) (redhat-SADP) | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| Red Hat | Red Hat OpenShift AI (RHOAI) | All | CVEProject cvelistV5 (CNA) |
| jupyter-server | jupyter_server | < 2.20 | CVEProject cvelistV5 (CNA) |
References and advisories
7- https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp x_refsource_CONFIRM
- https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-44727 vdb-entryx_refsource_REDHAT
- https://bugzilla.redhat.com/show_bug.cgi?id=2491516 issue-trackingx_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44727.json x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:43038 vendor-advisoryx_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:60520 vendor-advisoryx_refsource_REDHAT
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Details
- Published
- 2026-06-22
- Last updated
- 2026-08-28
- State
- Published
- Assigner (CNA)
- GitHub_M
Exploit prediction (EPSS)
0.43%
Probability of exploitation in 30 days
38.2%
Percentile (among all CVEs)
SSVC assessment (CISA)
- Automatable
- No
- Exploitation
- None
- Technical impact
- Total
Weaknesses (CWE)
- CWE-1021Improper Restriction of Rendered UI Layers or Frames
- CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')