CVE-2026-3514: Prefect Prefect Has An Authentication Middleware Vulnerability

HIGH
Advisory Identifier: GHSA-c635-393c-hcx2
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CVSS 7.5
CWE-863
Published
Advisory Summary

CVE-2026-3514 is a HIGH (CVSS 7.5) prefect has an authentication middleware vulnerability (CWE-863: Incorrect Authorization) affecting Prefect libraries in the PyPI ecosystem. The issue involves prefect has an authentication middleware bypass when url paths are appended with 'health' or 'ready'. Remediation is available by upgrading affected packages to version 3.6.22.dev7.

CVE-2026-3514 at a Glance

CVE Identifier CVE-2026-3514
GHSA Identifier GHSA-c635-393c-hcx2
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-863: Incorrect Authorization
Affected Product Prefect
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-3514

To remediate this vulnerability, upgrade all affected Prefect dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

prefect fixed: 3.6.22.dev7 
pip install prefect>=3.6.22.dev7
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show prefect

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-3514, inspect your installed packages using pip:

pip show prefect

Analyze the terminal output to locate any version of Prefect in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.6.22.dev7), your application is affected.

Note: The pip show prefect command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-863: Incorrect Authorization, where the product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. In Prefect, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2026-3514 Affected Prefect Versions

1 component(s)
Fixed Versions:
3.6.22.dev7
Product / Package Ecosystem Affected Versions Fixed Version
prefect
pypi/prefect
PyPI
< 3.6.22.dev7
3.6.22.dev7

References

NVD — CVE-2026-3514 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-3514
Security Fix Commit FIX COMMIT
https://github.com/prefecthq/prefect/commit/e21617125335025b4b27e7d6f0ca028e8e8f3b79
Prefect Source Repository REPOSITORY
https://github.com/PrefectHQ/prefect
huntr.com/bounties/c540e5e1-f... WEB
https://huntr.com/bounties/c540e5e1-f74f-44f4-bfa0-9764ff6daa75

Frequently Asked Questions

What is CVE-2026-3514?
CVE-2026-3514 is a security vulnerability in Prefect involving Prefect has an Authentication Middleware Bypass when URL paths are appended with 'health' or 'ready' under CWE-863: Incorrect Authorization.
Which Prefect versions are affected?
Affected versions include releases prior to 3.6.22.dev7 across affected packages: prefect.
What version fixes CVE-2026-3514?
Upgrading to 3.6.22.dev7 (or the latest patched release for your respective branch) resolves the vulnerability.
Is prefect affected?
Yes, prefect is affected in releases prior to 3.6.22.dev7. Upgrade your dependency to 3.6.22.dev7 or later.
What is the CVSS score of CVE-2026-3514?
CVE-2026-3514 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-3514?
CVE-2026-3514 is classified under CWE-863: Incorrect Authorization (The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.).
How can I check PyPI dependencies for CVE-2026-3514?
Run the dependency tree command: 'pip show prefect'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-c635-393c-hcx2",
  "modified" : "2026-07-09T20:53:13Z",
  "published" : "2026-06-02T09:36:15Z",
  "aliases" : [ "CVE-2026-3514" ],
  "summary" : "Prefect has an Authentication Middleware Bypass when URL paths are appended with 'health' or 'ready'",
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "prefect"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.6.22.dev7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-3514"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/prefecthq/prefect/commit/e21617125335025b4b27e7d6f0ca028e8e8f3b79"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/PrefectHQ/prefect"
  }, {
    "type" : "WEB",
    "url" : "https://huntr.com/bounties/c540e5e1-f74f-44f4-bfa0-9764ff6daa75"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-863" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-09T20:53:13Z",
    "nvd_published_at" : "2026-06-02T09:16:16Z"
  }
}