CVE-2018-16731: CScms 4.1 allows arbitrary file upload by (for example) adding the php extension to the default filetype list

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CRITICAL 9.8REMOTEDOWNGRADE

CVE-2018-16731 is a critical-severity flaw (CVSS 9.8) affecting cscms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

CScms 4.1 allows arbitrary file upload by (for example) adding the php extension to the default filetype list (gif, jpg, png), and then providing a .php pathname within fileurl JSON data.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.5% (top 26%)
CISA exploited list	No
Weakness	CWE-434
Published	2018-09-08
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: chshcms

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

Am I affected?

Timeline

2018-09-08 15:29 UTCPublished CVE record published
2026-06-17 01:44 UTCUpdated Record last modified

chshcms cscms DOWNGRADE

Affected: 4.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.1

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.1 (Debian / Ubuntu)

apt-cache madison cscms sudo apt install cscms=<VERSION_BEFORE_4.1> sudo apt-mark hold cscms

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

dnf --showduplicates list cscms sudo dnf downgrade cscms-<VERSION_BEFORE_4.1> sudo dnf versionlock add cscms

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-2018-16731?

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

Is CVE-2018-16731 being exploited?

CVE-2018-16731 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-2018-16731 affect?

CVE-2018-16731 affects cscms. Severity is critical (CVSS 9.8). CScms 4.1 allows arbitrary file upload by (for example) adding the php extension to the default filetype list (gif, jpg, png), and then providing a .php pathname within fileurl JSON data.

How urgent is CVE-2018-16731?

Priority 63/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

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References

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