CVE-2026-120338: PrefectHQ prefab-ui

Prefab UI Pyodide sandbox escape to host RCE

CVSS 10.0 CriticalCriticalEPSS 0.0077 · 55th percentile

Critical, because:

CVSS score 10.0: 9.0 or more.

Published by the CVE Program (CNA: JFROG) at 1 Nov 2026, 15:24 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
PrefectHQ	prefab-ui Package name: prefab-ui https://pypi.org/project/prefab-ui/	affected 0.14.0 to before 0.21.0 semver Other versions: unaffected

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
10.0	Critical	3.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H	CNA (JFROG)Used for this record
9.9	Critical	3.1	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H	CNA (JFROG)

CISA KEV Not listed.
EPSS 0.0077, the 55th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

1 Nov 2026, 15:24 UTC Confirmed by the CVE List
1 Nov 2026, 15:32 UTC First seen by agentprime
1 Nov 2026, 16:18 UTC Confirmed by NVD

Sources

References from the CNA

github.com/PrefectHQ/prefab product
pypi.org/project/prefab-ui/ product
github.com/PrefectHQ/prefab/security/advisories/GHSA-595q-jv4r-q7j9 vendor-advisory
github.com/PrefectHQ/prefab/pull/538 patch
github.com/PrefectHQ/prefab/commit/030f074f85e0b1be0dd44b0283185aecb26337a2 patch
github.com/PrefectHQ/prefab/releases/tag/v0.21.0 release-notes
pypi.org/project/prefab-ui/0.21.0/ release-notes
github.com/PrefectHQ/prefab/releases/tag/v0.20.2 technical-description
github.com/PrefectHQ/prefab/releases/tag/v0.14.0 technical-description

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.