VulnerabilityPublished 9 Dec 2025Updated 12 Dec 2025

CVE-2025-66625: Umbraco-CMS · Information Exposure

Affects Umbraco-CMSSource CVE Database V5

Not known to be exploited · CVSS 4.9 Medium : upgrade to 13.12.1 when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

4.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 29% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 13.12.1

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: High
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Umbraco-CMS to 13.12.1.

Affected software

Product	Affected	Fixed in
NuGetumbraco-cms`pkg:nuget/umbraco-cms`Other threats	Affected <13.12.1	Fixed in 13.12.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately upgrade all Umbraco CMS instances to version 13.12.1 or later to remediate this vulnerability. Until upgrades are applied, restrict backoffice access strictly to trusted personnel and enforce strong authentication mechanisms, including multi-factor authentication, to reduce the risk of credential compromise. Implement rigorous monitoring and alerting on backoffice access and unusual file system activity to detect exploitation attempts. Review and harden server configurations to ensure temporary files are securely handled and cleaned up promptly, minimizing residual sensitive data exposure. Consider network segmentation to isolate CMS servers from critical infrastructure and limit lateral movement opportunities. Additionally, audit Windows account privileges running the Umbraco application to follow the principle of least privilege, reducing the impact of potential NTLM hash exposure. Regularly update and patch all related infrastructure components and conduct penetration testing focusing on file enumeration and credential exposure vectors.

Description

Umbraco is an ASP.NET CMS. Due to unsafe handling and deletion of temporary files in versions 10.0.0 through 13.12.0, 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. This issue is fixed in version 13.12.1.

Impact

For European organizations using affected versions of Umbraco CMS, this vulnerability poses a risk of sensitive information exposure through file enumeration and potential NTLM hash leakage. Attackers with backoffice access could map the server filesystem, gaining insights into server configuration and potentially identifying further attack vectors. Exposure of NTLM hashes is particularly concerning in Windows-dominant environments common in Europe, as it can lead to credential compromise and lateral movement within corporate networks. This can result in unauthorized access to sensitive data, disruption of services, and increased risk of broader compromise. Organizations in sectors with high regulatory requirements, such as finance, healthcare, and government, face increased compliance risks if such exposures lead to data breaches. The requirement for authenticated access limits the threat to insiders or attackers who have already compromised user credentials, but the ease of file enumeration and hash exposure increases the risk of privilege escalation and extended network compromise.

CWE-200Exposure of Sensitive Information to an Unauthorized Actor (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #20OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
OWASP Cheat Sheets
Error Handling (opens in a new tab)
Logging (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.4 (opens in a new tab)
V14.3.3 (opens in a new tab)
V7.3.3 (opens in a new tab)
Attack patterns
Subverting Environment Variable Values (opens in a new tab)
ICMP Echo Request Ping (opens in a new tab)
TCP SYN Scan (opens in a new tab)
Enumerate Mail Exchange (MX) Records (opens in a new tab)
DNS Zone Transfers (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-377Insecure Temporary File (opens in a new tab)
Class weaknessOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
Creating and using insecure temporary files can leave application and system data vulnerable to attack.
OWASP Cheat Sheets
Authorization (opens in a new tab)
Attack patterns
Explore for Predictable Temporary File Names (opens in a new tab)
Screen Temporary Files for Sensitive Information (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-552Files or Directories Accessible to External Parties (opens in a new tab)
Base weaknessOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product makes files or directories accessible to unauthorized actors, even though they should not be.
Implementation · System Configuration · Operation
When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to disable public access.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.5.1 (opens in a new tab)
V12.4.1 (opens in a new tab)
V8.3.8 (opens in a new tab)
Attack patterns
Collect Data from Common Resource Locations (opens in a new tab)
Probe System Files (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 16 Dec 2025, 21:44 UTC

WeaknessesCWE-200, CWE-377, CWE-552

Technical details

References

Community reviews

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