CVE-2021-37770: Nucleus CMS v3.71 is affected by a file upload vulnerability

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HIGH 7.2DOWNGRADE

CVE-2021-37770 is a high-severity flaw (CVSS 7.2) affecting nucleus cms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Nucleus CMS v3.71 is affected by a file upload vulnerability. In this vulnerability, we can use upload to change the upload path to the path without the Htaccess file. Upload an Htaccess file and write it to AddType application / x-httpd-php.jpg. In this way, an attacker can upload a picture with shell, treat it as PHP, execute commands, so as to take down website resources.

Why this priority

High severity
Public exploit reference

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

Risk facts

CVSS score	7.2 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	None
EPSS exploit chance	1.3% (top 29%)
CISA exploited list	No
Weakness	CWE-434
Published	2022-06-30
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: nucleuscms

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

Am I affected?

Timeline

2022-06-30 15:15 UTCPublished CVE record published
2026-06-17 04:01 UTCUpdated Record last modified

nucleuscms nucleus cms DOWNGRADE

Affected: 3.71

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.71

1. Check installed version

apt-cache policy nucleus-cms || rpm -q nucleus-cms || nucleus-cms --version

2. No fixed release: DOWNGRADE to a release before 3.71 (Debian / Ubuntu)

apt-cache madison nucleus-cms sudo apt install nucleus-cms=<VERSION_BEFORE_3.71> sudo apt-mark hold nucleus-cms

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

dnf --showduplicates list nucleus-cms sudo dnf downgrade nucleus-cms-<VERSION_BEFORE_3.71> sudo dnf versionlock add nucleus-cms

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-2021-37770?

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

Is CVE-2021-37770 being exploited?

CVE-2021-37770 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-2021-37770 affect?

CVE-2021-37770 affects nucleus cms. Severity is high (CVSS 7.2). Nucleus CMS v3.71 is affected by a file upload vulnerability. In this vulnerability, we can use upload to change the upload path to the path without the Htaccess file. Upload an Htaccess file and write it to AddType application / x-httpd-ph

How urgent is CVE-2021-37770?

Priority 48/100. High severity; Public exploit reference

Software pages

Apache HTTP Server vulnerabilities · PHP vulnerabilities

Related CVEs

CVE-2018-16636 MEDIUM 6.5 DOWNGRADE Nucleus CMS 3.70 allows HTML Injection via the index.php body parameter.
CVE-2015-5454 MEDIUM 4.3 DOWNGRADE Cross-site scripting (XSS) vulnerability in Nucleus CMS allows remote attackers to inject arbitrary web script
CVE-2011-3760 MEDIUM 5.0 DOWNGRADE Nucleus 3.61 allows remote attackers to obtain sensitive information via a direct request to a .php file, whic
CVE-2009-0929 MEDIUM 5.0 UPGRADE Directory traversal vulnerability in the media manager in Nucleus CMS before 3.40 allows remote attackers to r

References

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