CVE-2021-37334
No exploitation reported by the sources we read.
- Published2021-08-25
- Fixed in8.7.6 · 8.6.2 · 8.5.7 · 8.4.4 · 8.3.4 · 8.2.3
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
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.
Timeline
dates in UTC- 2021-08-2522:15CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-37334?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-37334?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 8.7 | ≥ 8.7.0, < 8.7.6 | 8.7.6 | NVD |
| 8.6 | ≥ 8.6.0, < 8.6.2 | 8.6.2 | NVD |
| 8.5 | ≥ 8.5.0, < 8.5.7 | 8.5.7 | NVD |
| 8.4 | ≥ 8.4.0, < 8.4.4 | 8.4.4 | NVD |
| 8.3 | ≥ 8.3.0, < 8.3.4 | 8.3.4 | NVD |
| 8.2 | ≥ 8.2.0, < 8.2.3 | 8.2.3 | NVD |
| 8.1 | ≥ 8.1.0, < 8.1.6 | 8.1.6 | NVD |
| 8.0 | ≥ 8.0.0, < 8.0.2 | 8.0.2 | NVD |
| 7.5 | ≥ 7.5.0, < 7.5.4 | 7.5.4 | NVD |
| 7.4 | ≥ 7.4.0, < 7.4.3 | 7.4.3 | NVD |
| 7.3 | ≥ 7.3.0, < 7.3.2 | 7.3.2 | NVD |
| 7.2 | ≥ 7.2.0, < 7.2.1 | 7.2.1 | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
- Update Umbraco forms to 8.7.6 · 8.6.2 · 8.5.7 · 8.4.4 · 8.3.4 · 8.2.3 · 8.1.6 · 8.0.2
Advisories and patches
- umbraco.comPatch · Vendor Advisory
- umbraco.comVendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- NVDCVSS 3.19.8read 2026-10-23
- NVDCVSS 2.09.3read 2026-10-23
- FIRST EPSSEPSS score2.7 %2026-10-23
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Published
- 2021-08-25
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-37334?
Is CVE-2021-37334 actively exploited?
What is the CVSS score for CVE-2021-37334?
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.