Prefect has an Authentication Middleware Bypass when URL paths are appended with 'health' or 'ready'

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-3514: 0.48% estimated exploitation activity in the next 30 days; percentile 41.14 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

In version 3.6.19 of prefecthq/prefect, an authentication bypass vulnerability exists due to the improper handling of URL path exemptions for health check probes. Specifically, the authentication middleware exempts any URL path ending with 'health' or 'ready' from authentication checks. This allows an attacker to create resources with names ending in 'health' or 'ready' and access them without authentication. Affected endpoints include those for variables, flows, work pools, work queues, and deployments. This vulnerability can lead to unauthorized access to sensitive information, such as API keys and database credentials, stored in Prefect Variables.

Published by the source

2 Jun 2026, 09:36 UTC

Last modified by the source

10 Sep 2026, 03:51 UTC

Source last checked

26 Oct 2026, 13:46 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-c635-393c-hcx2

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-c635-393c-hcx2

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# Patch Next advisory brief: CVE-2026-3514

Advisory: Prefect has an Authentication Middleware Bypass when URL paths are appended with 'health' or 'ready'
IDs: CVE-2026-3514, GHSA-c635-393c-hcx2
Record: https://patchnext.com/advisories/cve-2026-3514 (revision 2, source checked 26 Oct 2026, 13:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: prefect 3.6.22.dev7. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI prefect: affected < 3.6.22.dev7; fixed in 3.6.22.dev7

## Suggested inspection (read-only)
- `python -m pip show prefect`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on prefect.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-c635-393c-hcx2 (OSV record GHSA-c635-393c-hcx2 lists affected ranges: PyPI prefect >=0 <3.6.22.dev7 (fixed))
- Verified: https://github.com/advisories/GHSA-c635-393c-hcx2 (GitHub-reviewed advisory GHSA-c635-393c-hcx2 lists affected ranges: PyPI prefect >=0 <3.6.22.dev7)

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