CVE-2021-27811Public exploitNetwork attack vector

Authenticated PHP code execution via upgrade-log injection

Published May 21, 2021 · Updated Aug 3, 2024

Code injection in QibosoftX1 1.0 allows remote authenticated users to execute arbitrary PHP code through the administrative upgrade endpoint. The Upgrade.php sysup function inserts the upgrade_edition query value without sanitization into runtime/client_upgrade_edition.php, which PHP later includes and evaluates. Administrative privileges are required, and successful exploitation writes a persistent PHP web shell with the web server's permissions.

CVSS severity7.2
High
EPSS probability1.20%
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

Code injection in QibosoftX1 1.0 allows remote authenticated users to execute arbitrary PHP code through the administrative upgrade endpoint. The Upgrade.php sysup function inserts the upgrade_edition query value without sanitization into runtime/client_upgrade_edition.php, which PHP later includes and evaluates. Administrative privileges are required, and successful exploitation writes a persistent PHP web shell with the web server's permissions.

The record

CVE
CVE-2021-27811
Published
May 21, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-94, T1505.003
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. May 21, 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

7.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDAV:N/AC:L/Au:S/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

CWE-94Improper Control of Generation of Code ('Code Injection')
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