CVE-2020-21366: Cross Site Request Forgery vulnerability in GreenCMS v.2.3 allows an attacker to gain privileges via the addus

Routine

HIGH 8.0DOWNGRADE

CVE-2020-21366 is a high-severity flaw (CVSS 8.0) affecting greencms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Cross Site Request Forgery vulnerability in GreenCMS v.2.3 allows an attacker to gain privileges via the adduser function of index.php.

Why this priority

High severity
Public exploit reference

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

Risk facts

CVSS score	8.0 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.3% (top 74%)
CISA exploited list	No
Weakness	CWE-352
Published	2023-06-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: njtech

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

Am I affected?

Timeline

2023-06-20 15:15 UTCPublished CVE record published
2026-06-17 03:03 UTCUpdated Record last modified

njtech greencms DOWNGRADE

Affected: 2.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.3 (Debian / Ubuntu)

apt-cache madison greencms sudo apt install greencms=<VERSION_BEFORE_2.3> sudo apt-mark hold greencms

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

dnf --showduplicates list greencms sudo dnf downgrade greencms-<VERSION_BEFORE_2.3> sudo dnf versionlock add greencms

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.

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-2020-21366?

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

Is CVE-2020-21366 being exploited?

CVE-2020-21366 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-2020-21366 affect?

CVE-2020-21366 affects greencms. Severity is high (CVSS 8.0). Cross Site Request Forgery vulnerability in GreenCMS v.2.3 allows an attacker to gain privileges via the adduser function of index.php.

How urgent is CVE-2020-21366?

Priority 39/100. High severity; Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2025-14244 LOW 2.4 DOWNGRADE A flaw has been found in GreenCMS 2.3.0603
CVE-2025-15187 LOW 3.8 UPGRADE A vulnerability was found in GreenCMS up to 2.3
CVE-2025-9415 MEDIUM 6.3 UPGRADE A vulnerability was identified in GreenCMS up to 2.3.0603
CVE-2024-22570 MEDIUM 5.4 DOWNGRADE A stored cross-site scripting (XSS) vulnerability in /install.php?m=install&c=index&a=step3 of GreenCMS v2.3 a
CVE-2022-28918 HIGH 8.1 DOWNGRADE GreenCMS v2.3.0603 was discovered to contain an arbitrary file deletion vulnerability via /index.php?m=admin&c

References

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