CVE-2025-66625 is a medium-severity security vulnerability in Umbraco.Cms (nuget), affecting versions >= 10.0.0, <= 13.12.0. It is fixed in 13.12.1.
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.
CVE-2025-66625 has a CVSS score of 4.9 (Medium). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (13.12.1). Upgrading removes the vulnerable code path.
nuget
Umbraco.Cms (>= 10.0.0, <= 13.12.0)Umbraco.Cms → 13.12.1 (nuget)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2025-66625 is reachable in your applications. Explore open-source security for your team.
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Upgrade Umbraco.Cms to 13.12.1 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2025-66625 is a medium-severity security vulnerability in Umbraco.Cms (nuget), affecting versions >= 10.0.0, <= 13.12.0. It is fixed in 13.12.1.
CVE-2025-66625 has a CVSS score of 4.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Umbraco.Cms (nuget) versions >= 10.0.0, <= 13.12.0 is affected.
Yes. CVE-2025-66625 is fixed in 13.12.1. Upgrade to this version or later.
Whether CVE-2025-66625 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade Umbraco.Cms to 13.12.1 or later.