CVE-2026-54611

InstantCMS has Remote Code Execution in package installer

MEDIUM
5.5
CVSS Score
Published: September 8, 2026 at 05:16 PM UTC
Updated: September 9, 2026 at 06:16 PM UTC
1 product affected across 1 vendorInstantcms

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Severity
MEDIUM5.5
Exploit prediction
EPSS 0.7%
SSVC
PoC

Description

InstantCMS is a free and open source content management system. Versions prior to 2.18.2 have a Remote Code Execution (RCE) issue that allows remote authenticated attackers to execute any PHP code via the component installer. It is possible to upload a malicious component into the server, however, it won't be installed, but upload files will be executed. Normally all php files in upload folder are not executed, however, by uploading custom .htaccess it becomes possible. Version 2.18.2 contains a fix.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 2.18.2
Affected range stops below 2.18.2, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.5MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
HIGH
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-94CWE-434

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