A cross‑site scripting flaw in the Dask distributed dashboard, visible when accessed through the Jupyter Lab proxy, allows an attacker to craft a URL that causes the default Jupyter Python kernel to execute arbitrary code. This gives the attacker remote execution rights on the host running Jupyter, potentially compromising confidentiality, integrity, and availability of the entire distributed environment. The weakness is an XSS flaw (CWE‑79, CWE‑80) with a privilege escalation element (CWE‑250).

The vulnerability affects installations of dask distributed older than version 2026.1.0 that run alongside Jupyter Lab or jupyter‑server‑proxy. Any user environment that uses the default localhost ports to expose the dashboard—across Linux, Windows, or macOS—is susceptible, regardless of the Python distribution used.

The CVSS score of 5.3 indicates moderate severity, while the EPSS score of less than 1% suggests exploitation is currently improbable. The CVE is not listed in the CISA KEV catalog, and no public exploit has been confirmed. The attack vector requires user interaction: a malicious link must be clicked within a Jupyter Lab session that has a running Dask dashboard. Once accessed, code runs with the privileges of the Jupyter kernel—often full system privileges—so a single compromised user could potentially compromise an entire cluster. Although realistic risk is low, the impact of successful exploitation is high, warranting prompt remediation.