Vulnerability report

Exploited in the wild High confidence Not in CISA KEV

CVE-2020-27387

HorizontCMS

HorizontCMS

Watch CVE-2020-27387 Browse KEV feed
Severity
CVSS 8.8 · High
Confidence
High
Exploit status
Exploited in the wild
EPSS
18.5%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2020-27387 is a vulnerability affecting HorizontCMS. An unrestricted file upload issue in HorizontCMS through 1.0.0-beta allows an authenticated remote attacker (with access to the FileManager) to upload and...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is high. Also confirmed by third-party sources.

Who is affected?

HorizontCMS.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

HorizontCMS

An unrestricted file upload issue in HorizontCMS through 1.0.0-beta allows an authenticated remote attacker (with access to the FileManager) to upload and execute arbitrary PHP code by uploading a PHP payload, and then using the FileManager's rename function to provide the payload (which will receive a random name on the server) with the PHP extension, and finally executing the PHP file via an HTTP GET request to /storage/.

NOTE: the vendor has patched this while leaving the version number at 1.0.0-beta.

Published
05 Nov 2020
Exploitation Reported
05 Nov 2020
Attack vector
Remote
Complexity
Low
Privileges
Low
User interaction
None

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

The Shadowserver

Recorded 05 Nov 2020

A trusted third party reported exploitation.

Proof of concept available

Recorded 28 Apr 2025

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
The Shadowserver First 2020-11-05 01:18 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Metasploit https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/multi/http/horizontcms_upload_exec.rb 28 Apr 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

8.8 High

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

18.5%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Unrestricted Upload of File with Dangerous Type CWE-434

All CVSS Scores

CVSS v3.1 8.8 High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v2.0 6.5 Medium

AV:N/AC:L/Au:S/C:P/I:P/A:P

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

horizontcms_upload_exec

metasploit · Created Unknown

Metasploit module for CVE-2020-27387

Timeline

From disclosure to observed exploitation

  1. 15:02 UTC

    Metasploit module available

    Exploit module available

  2. 15:02 UTC

    Public PoC available

    Public proof-of-concept code published

  3. 01:18 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  4. 01:18 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 00:00 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2020-27387

Sample API response 
{
  "cve_id": "CVE-2020-27387",
  "confidence": "High",
  "cvss_score": 8.8,
  "cvss_estimated": false,
  "epss_score": 0.18461,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}