CVE-2021-37334

What it is

Umbraco Forms version 4.0.0 up to and including 8.7.5 and below are vulnerable to a security flaw that could lead to a remote code execution attack and/or arbitrary file deletion. A vulnerability occurs because validation of the file extension is performed after the file has been stored in a temporary directory. By default, files are stored within the application directory structure at %BASEDIR%/APP_DATA/TEMP/FileUploads/. Whilst access to this directory is restricted by the root web.config file, it is possible to override this restriction by uploading another specially crafted web.config file to the temporary directory. It is possible to exploit this flaw to upload a malicious script file to execute arbitrary code and system commands on the server.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

2.7% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-08-25 22:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:00 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 2.7% in the next 30 days (EPSS).
• Severity: 9.8 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-08-25 22:15 UTC

Last modified

2026-06-17 04:00 UTC

Exploit probability

2.7% · EPSS, next 30 days

Record status

Modified

Affected

• Umbraco Forms < 4.4.9
• Umbraco Forms < 6.0.10
• Umbraco Forms < 7.0.7
• Umbraco Forms < 7.1.4
• Umbraco Forms < 7.2.1
• Umbraco Forms < 7.3.2
• Umbraco Forms < 7.4.3
• Umbraco Forms < 7.5.4

Attack profile CVSS 3.1 · 9.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-37334.md and follow it. Check whether this project is affected by CVE-2021-37334. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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