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CRITICAL severity

CVE-2021-3378 — Fortilogger

CRITICAL

CVE-2021-3378 is a critical-severity (CVSS 9.8) Unrestricted File Upload vulnerability in fortilogger fortilogger. 7 public exploit references exist, so weaponization risk is real. A fix is available — see the affected versions and patch details below.

FortiLogger 4.4.2.2 is affected by Arbitrary File Upload by sending a "Content-Type: image/png" header to Config/SaveUploadedHotspotLogoFile and then visiting Assets/temp/hotspot/img/logohotspot.asp.

Published
Updated
Affected
1 product
Patched
See advisory
Exploits
7 known
Exploitation data as of Oct 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
97.5%probability of exploitation in next 30 days
Very High Risk0.00%
Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk
91.4%93.9%96.4%98.9%92.8%97.5%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-3378 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 394,415 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.

Description

FortiLogger 4.4.2.2 is affected by Arbitrary File Upload by sending a "Content-Type: image/png" header to Config/SaveUploadedHotspotLogoFile and then visiting Assets/temp/hotspot/img/logohotspot.asp.

Affected Products

1 product · 1 configurations
Application
fortiloggerfortilogger
< 5.2.0
range
Exploits & PoCs
7

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-49600webappsmultiple✓ Verified

FortiLogger 4.4.2.2 - Unauthenticated Arbitrary File Upload (Metasploit)

by Berkan Er · Mar 1, 2021

Exploit-DB Source

Detection & mitigation playbook

Vendor / appliance

  1. Detect

    Inventory every fortilogger fortilogger deployment and check each version against the affected-products list above.

  2. Fix

    Apply the fortilogger fortilogger security patch or hotfix for CVE-2021-3378 on the affected version, following the vendor advisory for your exact build.

  3. Workarounds

    Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

How to detect CVE-2021-3378

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2021-3378 -u https://target
Template
FortiLogger 4.4.2.2 - Arbitrary File Upload
Severity
critical
Impact
Successful exploitation of this vulnerability could result in unauthorized access, remote code execution, and potential compromise of the affected system.
Remediation
Apply the latest security patch or upgrade to a patched version of FortiLogger to mitigate this vulnerability.

Template by ProjectDiscovery nuclei-templates (dwisiswant0), MIT licensed. View the full template. Scan only systems you are authorised to test.

Frequently Asked Questions

FortiLogger 4.4.2.2 is affected by Arbitrary File Upload by sending a "Content-Type: image/png" header to Config/SaveUploadedHotspotLogoFile and then visiting Assets/temp/hotspot/img/logohotspot.asp.
O3 Security · Runtime Protection

Is CVE-2021-3378 being exploited in your environment?

Detect and block the exploit chain at execution, on systems you cannot patch yet.

Protect my workloads How runtime protection works
CVE-2021-3378: Fortilogger (Critical 9.8)