GHSA-c635-393c-hcx2 is a high-severity (CVSS 7.5) CWE-863 vulnerability in prefect. O3 Security confirms whether GHSA-c635-393c-hcx2 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Prefect has an Authentication Middleware Bypass when URL paths are appended with 'health' or 'ready'
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-c635-393c-hcx2.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-c635-393c-hcx2 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 0 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
prefectReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | prefect | all versions | 3.6.22.dev7 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for prefect. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update prefect to 3.6.22.dev7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c635-393c-hcx2 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-c635-393c-hcx2 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-c635-393c-hcx2. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-c635-393c-hcx2 in your dependencies?
O3 detects GHSA-c635-393c-hcx2 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.