CVE-2025-66625 is a medium-severity (CVSS 4.9) Information Exposure vulnerability in Umbraco.Cms. A fix is available for Umbraco.Cms — see the affected versions and patch details below.
Umbraco Vulnerable to Improper File Access and Credential Exposure through Dictionary Import Functionality
Exploitation Status
No confirmed exploitation observed yet
- 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 CVE-2025-66625.
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
CVE-2025-66625 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 378,567 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.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
Impact
Due to unsafe handling and deletion of temporary files during the dictionary upload process, an attacker with access to the backoffice can trigger predictable requests to temporary file paths. The application’s error responses (HTTP 500 when a file exists, 404 when it does not) allow the attacker to enumerate the existence of arbitrary files on the server’s filesystem. This vulnerability does not allow reading or writing file contents.
In certain configurations, incomplete clean-up of temporary upload files may additionally expose the NTLM hash of the Windows account running the Umbraco application. The direct impact of this vulnerability is therefore limited to confidentiality, which is reflected in its CVSS base score of 4.9
While the CVSS Base Score captures only the immediate effect, the practical risk varies significantly based on hosting environment and identity configuration. Umbraco Cloud sites run under low-privilege, isolated Azure App Service worker identities, which mitigates the impact of any credential exposure. In contrast, self-hosted deployments could run Umbraco using privileged local or domain accounts. If such an account’s NTLM hash is disclosed, an attacker may be able to:
- Perform NTLM relay attacks
- Crack the hash offline to recover the underlying password
- Authenticate as the compromised identity
- Access internal systems trusted by that identity
- Move laterally within the network
- Potentially escalate to full domain compromise in weakly segmented environments
These outcomes are not part of the CVSS base score, which only rates the immediate confidentiality impact, but represent realistic downstream consequences for installations using elevated or widely-trusted service accounts. Self-hosted environments running Umbraco under privileged identities are therefore at significantly higher risk.
Vulnerability found and reported by Tomasz Holeksa at Pentest Limited
Patches
The issue has been patched in 13.12.1.
Workarounds
The issue can only be exploited by authorized backoffice accounts with access to the "Translations" section.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Umbraco.Cms | ≥ 10.0.0&&< 13.12.1 | 13.12.1dotnet add package Umbraco.Cms --version 13.12.1 |
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 13.12.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66625 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 CVE-2025-66625 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-66625. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-66625 in your dependencies?
O3 Security finds CVE-2025-66625 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.