CVE-2026-56290: Joomlack Page Builder Improper Access Control Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Joomlack Page Builder. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-07-07, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-07-10; treat that as the outer limit, not the target.
• EPSS 30.9%, percentile 98: FIRST’s model estimates a 30.9% chance of exploitation activity in the next 30 days, higher than 98% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Editorial verdict: Check exposure. Page Builder CK CVE-2026-56290: Exploited Joomla Upload RCE — Only Joomla sites running Page Builder CK are at risk, but for them this is an emergency: an unauthenticated web-shell upload exploited within hours of the patch, with an incomplete first fix, so update to 3.6.5 or later and hunt for shells.

What it is

Joomla Extension - joomlack.fr - Unauthenticated file upload in Page Builder CK extension

CISA’s summary

Joomlack Page Builder contains an improper access control vulnerability that could allow for remote code execution via unauthenticated arbitrary file upload.

Weakness type: CWE-434, CWE-284.

Product: Joomlack Page Builder · Assigned by: Joomla · Published: 2026-06-29

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2026-07-07; federal due date 2026-07-10. Known ransomware use: Unknown.
• CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
• CISA SSVC assessment: exploitation active, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 30.87% probability of exploitation activity in the next 30 days; percentile 98.

Timeline

• 2026-06-27 — erroneo.us brief: Page Builder CK CVE-2026-56290: Exploited Joomla Upload RCE
• 2026-06-29 — CVE record published by Joomla
• 2026-07-07 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2026-07-10 — CISA remediation deadline for US federal agencies
• 2026-10-08 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. forum.joomlack.fr forum.joomlack.fr
2. Listed in CISA KEV notes (joomlack.fr) joomlack.fr

Vulnerability records

1. CVE.org record CVE-2026-56290 cve.org
2. NVD entry CVE-2026-56290 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov
2. Listed in CISA KEV notes (cisa.gov) cisa.gov
3. Listed in CISA KEV notes (cisa.gov) cisa.gov

Other references from the CVE record and advisory

1. joomlack.fr joomlack.fr
2. mysites.guru mysites.guru

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