CVE-2021-40902: flatCore-CMS version 2.0.8 is affected by Cross Site Scripting (XSS) in the "Create New Page" option through t

Routine

MEDIUM 5.4DOWNGRADE

CVE-2021-40902 is a medium-severity flaw (CVSS 5.4) affecting flatcore-cms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

flatCore-CMS version 2.0.8 is affected by Cross Site Scripting (XSS) in the "Create New Page" option through the index page.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.5% (top 59%)
CISA exploited list	No
Weakness	CWE-79
Published	2022-06-13
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: flatcore

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

Am I affected?

Timeline

2022-06-13 13:15 UTCPublished CVE record published
2026-06-17 04:07 UTCUpdated Record last modified

flatcore flatcore-cms DOWNGRADE

Affected: 2.0.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0.8

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.0.8 (Debian / Ubuntu)

apt-cache madison flatcore-cms sudo apt install flatcore-cms=<VERSION_BEFORE_2.0.8> sudo apt-mark hold flatcore-cms

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

dnf --showduplicates list flatcore-cms sudo dnf downgrade flatcore-cms-<VERSION_BEFORE_2.0.8> sudo dnf versionlock add flatcore-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-2021-40902?

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

Is CVE-2021-40902 being exploited?

CVE-2021-40902 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-2021-40902 affect?

CVE-2021-40902 affects flatcore-cms. Severity is medium (CVSS 5.4). flatCore-CMS version 2.0.8 is affected by Cross Site Scripting (XSS) in the "Create New Page" option through the index page.

How urgent is CVE-2021-40902?

Priority 34/100. Public exploit reference

Related CVEs

CVE-2022-43118 MEDIUM 6.1 DOWNGRADE A cross-site scripting (XSS) vulnerability in flatCore-CMS v2.1.0 allows attackers to execute arbitrary web sc
CVE-2021-42245 MEDIUM 6.1 DOWNGRADE FlatCore-CMS 2.0.9 has a cross-site scripting (XSS) vulnerability in pages.edit.php through meta tags and cont
CVE-2021-41403 CRITICAL 9.8 DOWNGRADE flatCore-CMS version 2.0.8 calls dangerous functions, causing server-side request forgery vulnerabilities.
CVE-2021-41402 HIGH 8.8 DOWNGRADE flatCore-CMS v2.0.8 has a code execution vulnerability, which could let a remote malicious user execute arbitr

References

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