CVE-2021-41403: flatCore-CMS version 2.0.8 calls dangerous functions, causing server-side request forgery vulnerabilities.

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2021-41403 is a critical-severity flaw (CVSS 9.8) 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 calls dangerous functions, causing server-side request forgery vulnerabilities.

Why this priority

Critical severity
EPSS top 3%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	19.1% (top 3%)
CISA exploited list	No
Weakness	CWE-918
Published	2022-06-15
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

2022-06-15 22:15 UTCPublished CVE record published
2026-06-17 04:08 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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora ELN · luksmeta · FIXED · 11-3.eln159 · FEDORA-2026-5176083b78 · source

sudo dnf upgrade --advisory=FEDORA-2026-5176083b78

Fedora 46 · openscad · FIXED · 2021.01-34.fc46 · FEDORA-2026-faf1721128 · source

sudo dnf upgrade --advisory=FEDORA-2026-faf1721128

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-2021-41403?

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

Is CVE-2021-41403 being exploited?

CVE-2021-41403 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-2021-41403 affect?

CVE-2021-41403 affects flatcore-cms. Severity is critical (CVSS 9.8). flatCore-CMS version 2.0.8 calls dangerous functions, causing server-side request forgery vulnerabilities.

How urgent is CVE-2021-41403?

Priority 69/100. Critical severity; EPSS top 3%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

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-2021-41402 HIGH 8.8 DOWNGRADE flatCore-CMS v2.0.8 has a code execution vulnerability, which could let a remote malicious user execute arbitr
CVE-2021-40902 MEDIUM 5.4 DOWNGRADE flatCore-CMS version 2.0.8 is affected by Cross Site Scripting (XSS) in the "Create New Page" option through t

References

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