CVE-2026-120338: PrefectHQ prefab-ui · Protection Mechanism Failure
Affects PrefectHQ prefab-uiSource CVE Database V5
Not known to be exploited · CVSS 10.0 Critical : upgrade to 0.21.0 as a priority.
Data as of 1 Nov 2026, 15:45 UTC
Thin evidence
One scorer or none| CNA (JFROG) | CVSS 3.1 | 10.0 |
|---|---|---|
| CNA (JFROG) | CVSS 3.1 | 9.9 |
- Patch
- Available – fixed in 0.21.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 1 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 1 Nov 2026.
What to do
Upgrade PrefectHQ prefab-ui to 0.21.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| PrefectHQprefab-ui | Affected
| Fixed in
|
PyPIprefab-uipkg:pypi/prefab-uiOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Upgrade prefab-ui to version 0.21.0 or later, where the vulnerability is fixed by revoking Deno read, write, and network permissions before accepting untrusted code and restricting network access to cdn.jsdelivr.net. Ensure that authentication is properly configured to restrict access to the Generative UI tool.
Description
PrefabHQ prefab-ui versions 0.14.0 through 0.20.2 contain a critical protection mechanism failure in their Generative UI sandbox. The sandbox runs caller-supplied Python code inside Pyodide within a Deno subprocess but starts Deno with unrestricted read, write, and network permissions. This allows an attacker supplying code to read and write files as the server OS user and persist code execution by writing files into the server's virtual environment. The vulnerability is fixed in version 0.21.0 by revoking these permissions before accepting code and restricting network access.
References
- github.com/PrefectHQ/prefab (opens in a new tab)
- pypi.org/project/prefab-ui/ (opens in a new tab)
- github.com/PrefectHQ/prefab/security/advisories/GHSA-595q-jv4r-q7j9 (opens in a new tab)
- github.com/PrefectHQ/prefab/pull/538 (opens in a new tab)
- github.com/PrefectHQ/prefab/commit/030f074f85e0b1be0dd44b0283185aecb26337a2 (opens in a new tab)
- github.com/PrefectHQ/prefab/releases/tag/v0.21.0 (opens in a new tab)
- pypi.org/project/prefab-ui/0.21.0/ (opens in a new tab)
- github.com/PrefectHQ/prefab/releases/tag/v0.20.2 (opens in a new tab)
- github.com/PrefectHQ/prefab/releases/tag/v0.14.0 (opens in a new tab)