CVE-2020-27387: An unrestricted file upload issue in HorizontCMS through 1.0.0-beta allows an authenticated remote attacker (w

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HIGH 8.8DOWNGRADE

CVE-2020-27387 is a high-severity flaw (CVSS 8.8) affecting horizontcms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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/<php_file_name>. NOTE: t

Why this priority

High severity
EPSS top 3%: very likely to be exploited
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	18.5% (top 3%)
CISA exploited list	No
Weakness	CWE-434
Published	2020-11-05
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: horizontcms project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-11-05 02:15 UTCPublished CVE record published
2026-06-17 03:09 UTCUpdated Record last modified

horizontcms project horizontcms DOWNGRADE

Affected: 1.0.0 alpha · 1.0.0 alpha2 · 1.0.0 alpha3 · 1.0.0 alpha4 · 1.0.0 alpha5 · 1.0.0 alpha6 · 1.0.0 alpha7 · 1.0.0 alpha8

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0.0

1. Check installed version

apt-cache policy horizontcms || rpm -q horizontcms || horizontcms --version

2. No fixed release: DOWNGRADE to a release before 1.0.0 (Debian / Ubuntu)

apt-cache madison horizontcms sudo apt install horizontcms=<VERSION_BEFORE_1.0.0> sudo apt-mark hold horizontcms

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list horizontcms sudo dnf downgrade horizontcms-<VERSION_BEFORE_1.0.0> sudo dnf versionlock add horizontcms

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Metasploit: HorizontCMS Arbitrary PHP File Upload

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-27387?

horizontcms: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-27387 being exploited?

CVE-2020-27387 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-27387 affect?

CVE-2020-27387 affects horizontcms. Severity is high (CVSS 8.8). 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

How urgent is CVE-2020-27387?

Priority 60/100. High severity; EPSS top 3%: very likely to be exploited; Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2022-25104 HIGH 7.5 DOWNGRADE HorizontCMS v1.0.0-beta.2 was discovered to contain an arbitrary file download vulnerability via the component
CVE-2021-28428 CRITICAL 9.8 DOWNGRADE File upload vulnerability in HorizontCMS before 1.0.0-beta.3 via uploading a .htaccess and *.hello files using
CVE-2020-28693 HIGH 8.8 DOWNGRADE An unrestricted file upload issue in HorizontCMS 1.0.0-beta allows an authenticated remote attacker to upload

References

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