MEDIUMPyPI →
Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP
Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP
Affected packages
- jupyter-server— before 2.20.0
Exploit signal
- Known exploited (CISA KEV)
- No
- EPSS score
- —
- EPSS percentile
- —
EPSS is the probability a CVE is exploited in the wild; percentile is its rank among all CVEs.
Sources
- https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-fcw5-x6j4-ccmp
- https://nvd.nist.gov/vuln/detail/CVE-2026-44727
- https://github.com/jupyter-server/jupyter_server/commit/6cbee8d65e71abac851c4492fea987ad080580bd
- https://access.redhat.com/errata/RHSA-2026:43038
- https://access.redhat.com/errata/RHSA-2026:60520
- https://access.redhat.com/security/cve/CVE-2026-44727
- https://bugzilla.redhat.com/show_bug.cgi?id=2491516
- https://github.com/advisories/GHSA-fcw5-x6j4-ccmp
- https://github.com/jupyter-server/jupyter_server
- https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2026-366.yaml
- https://pypi.org/project/jupyter-server
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44727.json
Structured record: https://osv.dev/vulnerability/GHSA-fcw5-x6j4-ccmp
Recommended response stack
Snyk — Scan your dependencies in CI and fix this vulnerability.→Socket — Detect malicious and compromised packages before they ship.→
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