CVE-2021-37334
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (2.74%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 2.74% probability · 86th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- umbraco/forms
- Source
- cve@mitre.org
EPSS 2.7% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://umbraco.com/blog/security-advisory-20th-of-july-2021-patch-is-now-available/Patch, Vendor Advisory
- https://umbraco.com/blog/security-advisory-security-patches-for-umbraco-forms-ready-on-july-20th-2021-at-7-am-utc/Vendor Advisory
- https://umbraco.com/blog/security-advisory-20th-of-july-2021-patch-is-now-available/Patch, Vendor Advisory
- https://umbraco.com/blog/security-advisory-security-patches-for-umbraco-forms-ready-on-july-20th-2021-at-7-am-utc/Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.