CVE-2021-27983Public exploitNetwork attack vector

Authenticated code execution via editable PHP documents

Published Dec 10, 2021 · Updated Aug 3, 2024

Remote code execution in MaxSite CMS 107.5 allows remote authenticated users to execute PHP through the Documents page. The Documents editor saves attacker-supplied PHP into a selected site file without blocking executable server-side content. Administrator access is required, and opening the Templates page executes the saved PHP in the CMS server context.

CVSS severity9.8
Critical
EPSS probability3.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Remote code execution in MaxSite CMS 107.5 allows remote authenticated users to execute PHP through the Documents page. The Documents editor saves attacker-supplied PHP into a selected site file without blocking executable server-side content. Administrator access is required, and opening the Templates page executes the saved PHP in the CMS server context.

The record

CVE
CVE-2021-27983
Published
Dec 10, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1505.003
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Dec 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1505.003Server Software Component: Web Shell

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo