GHSA-hmg4-wwm5-p999 is a medium-severity (CVSS 5.3) Information Exposure vulnerability in Umbraco.Cms. A fix is available for Umbraco.Cms — see the affected versions and patch details below.
Umbraco Allows User Enumeration Feasible Based On Management API Timing and Response Codes
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-hmg4-wwm5-p999.
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-hmg4-wwm5-p999 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 377,333 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
Umbraco.Cms.NETUmbraco.CmsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
Umbraco is a free and open source .NET content management system. Starting in version 14.0.0 and prior to versions 14.3.2 and 15.1.2, it's possible to determine whether an account exists based on an analysis of response codes and timing of Umbraco management API responses. Versions 14.3.2 and 15.1.2 contain a patch. No known workarounds are available.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Umbraco.Cms | ≥ 14.0.0&&< 14.3.2 | 14.3.2dotnet add package Umbraco.Cms --version 14.3.2 |
| .NETNuGet | Umbraco.Cms | ≥ 15.0.0&&< 15.1.2 | 15.1.2dotnet add package Umbraco.Cms --version 15.1.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Umbraco.Cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Umbraco.Cms to 14.3.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hmg4-wwm5-p999 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-hmg4-wwm5-p999 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-hmg4-wwm5-p999. 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-hmg4-wwm5-p999 in your dependencies?
O3 Security finds GHSA-hmg4-wwm5-p999 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.