Umbraco Forms
CVE-2021-33224
CRITICAL
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V5 - File Handling File type validation, storage isolation
MITRE ATT&CK
2 techniques across 2 tactics: Command and Control, Persistence The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. EPSS exploitation probability: 0.74%. |
| Exploit ScenarioDerived | A remote attacker could upload malicious files that can be executed on the server by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability. |
Get an e-mail when this CVE is exploited, patched or re-scored. Free account.
Alert meAnalysisAI
File upload vulnerability in Umbraco Forms v.8.7.0 allows unauthenticated attackers to execute arbitrary code via a crafted web.config and asp file. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
RemediationAI
No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Validate file types server-side, store uploads outside webroot, use random filenames, scan for malware.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as Unrestricted File Upload (CWE-434), which allows attackers to upload malicious files that can be executed on the server. File upload vulnerability in Umbraco Forms v.8.7.0 allows unauthenticated attackers to execute arbitrary code via a crafted web.config and asp file. Affected products include: Umbraco Umbraco Forms.
Know when Umbraco Forms gets its next vulnerability
- Watch products and get an email when something new is published
- Check this CVE against your own stack and servers
- Exploit and PoC references, threat intelligence from 22 sources
No credit card · 7-day full trial
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
File upload vulnerability in Umbraco Forms v.8.7.0 allows unauthenticated attackers to execute arbitrary code via a crafted web.config and asp file.
Threat Intelligence Overview
NVD
CVE.org
EPSS
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Malicious file upload attacks exploit insufficient validation when web applications accept user-provided files.
Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.
Affected Products (CPE)NVD
More in Umbraco Forms
View allUmbraco Forms versions up to 8.13.16 is affected by inclusion of functionality from untrusted control sphere (CVSS 7.5).
This affects all versions of package UmbracoForms. Rated high severity (CVSS 7.5), this vulnerability is remotely exploi
Authenticated users in Umbraco Forms versions 16 and 17 can exploit a path traversal vulnerability to read arbitrary fil
Umbraco Forms is a form builder that integrates with the Umbraco content management system. Rated low severity (CVSS 2.3
Umbraco Commerce is an open source dotnet web forms solution. Rated medium severity (CVSS 5.4), this vulnerability is re
Umbraco.Forms is a web form framework written for the nuget ecosystem. Rated medium severity (CVSS 5.8), this vulnerabil
GitHub PoC
Exploit-DB