CVE-2021-47753: phpKF CMS 3.00 Beta y6 contains an unauthenticated file upload vulnerability that allows remote attackers to e

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2021-47753 is a critical-severity flaw (CVSS 9.8) affecting cms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

phpKF CMS 3.00 Beta y6 contains an unauthenticated file upload vulnerability that allows remote attackers to execute arbitrary code by bypassing file extension checks. Attackers can upload a PHP file disguised as a PNG, rename it, and execute system commands through a crafted web shell parameter.

Why this priority

Critical severity
Public exploit reference
CISA SSVC: automatable with total technical impact
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	0.8% (top 44%)
CISA exploited list	No
Weakness	CWE-434
Published	2026-01-15
Last modified	2026-06-17

Publisher (CNA): VulnCheck · Vendor: phpkf

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

Am I affected?

Timeline

2026-01-15 16:16 UTCPublished CVE record published
2026-06-17 04:18 UTCUpdated Record last modified

phpkf cms DOWNGRADE

Affected: 3.00 beta_y6

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.00

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.00 (Debian / Ubuntu)

apt-cache madison cms sudo apt install cms=<VERSION_BEFORE_3.00> sudo apt-mark hold cms

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

dnf --showduplicates list cms sudo dnf downgrade cms-<VERSION_BEFORE_3.00> sudo dnf versionlock add 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 46 · jgmenu · FIXED · 4.7.0-1.fc46 · FEDORA-2026-3053ee4399 · source

sudo dnf upgrade --advisory=FEDORA-2026-3053ee4399

Fedora ELN · python-tkrzw · FIXED · 0.1.32-12.eln159 · FEDORA-2026-0161d71544 · source

sudo dnf upgrade --advisory=FEDORA-2026-0161d71544

Public exploits and detection

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

Write-up: www.exploit-db.com/exploits/50610

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-2021-47753?

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

Is CVE-2021-47753 being exploited?

CVE-2021-47753 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-2021-47753 affect?

CVE-2021-47753 affects cms. Severity is critical (CVSS 9.8). phpKF CMS 3.00 Beta y6 contains an unauthenticated file upload vulnerability that allows remote attackers to execute arbitrary code by bypassing file extension checks. Attackers can upload a PHP file disguised as a PNG, rename it, and execu

How urgent is CVE-2021-47753?

Priority 61/100. Critical severity; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

Related CVEs

CVE-2025-67443 MEDIUM 6.1 UPGRADE Schlix CMS before v2.2.9-5 is vulnerable to Cross Site Scripting (XSS)
CVE-2025-6736 MEDIUM 6.3 DOWNGRADE A vulnerability classified as critical was found in juzaweb CMS 3.4.2
CVE-2025-6735 MEDIUM 6.3 DOWNGRADE A vulnerability classified as critical has been found in juzaweb CMS 3.4.2
CVE-2025-5429 MEDIUM 6.3 UPGRADE A vulnerability classified as critical was found in juzaweb CMS up to 3.4.2
CVE-2025-5428 MEDIUM 6.3 UPGRADE A vulnerability classified as critical has been found in juzaweb CMS up to 3.4.2

References

← Back to latest CVEs