CVE-2026-54611Public exploitNetwork attack vector

Authenticated PHP execution via uploaded .htaccess override

Published Sep 8, 2026 · Updated Sep 9, 2026

Code injection in InstantCMS before 2.18.2 allows remote authenticated users to execute arbitrary PHP through the component installer. The installer extracts attacker-supplied PHP and a custom .htaccess file beneath its web-accessible upload directory, where the override re-enables PHP handling. Administrative installer access is required; successful exploitation executes code with the web server account's permissions.

CVSS severity5.5
Medium
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in InstantCMS before 2.18.2 allows remote authenticated users to execute arbitrary PHP through the component installer. The installer extracts attacker-supplied PHP and a custom .htaccess file beneath its web-accessible upload directory, where the override re-enables PHP handling. Administrative installer access is required; successful exploitation executes code with the web server account's permissions.

The record

CVE
CVE-2026-54611
Published
Sep 8, 2026
Updated
Sep 9, 2026
Vendor
InstantCMS Team
Product
InstantCMS
Classifications
CWE-434, CWE-94, T1505.003
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.18.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

InstantCMS Team · InstantCMSversion=< 2.18.2

Published CVSS scores

5.5GitHub Maintainer AdvisoryCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:H

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.

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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-434Unrestricted Upload of File with Dangerous Type
CWE-94Improper Control of Generation of Code ('Code Injection')
T1505.003Web Shell

Public exploit references

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

Technologies

Your stack

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Your stack

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