Security readout for executives and security teams
Plain-English summary
CVE-2026-56290 affects the Joomla Page Builder CK extension from joomlack.fr. It allows unauthenticated attackers to upload executable files, which can lead to full remote code execution. CISA KEV listing indicates exploitation is known. Public-facing Joomla sites using this extension should be treated as urgent.
Executive priority
Treat as emergency remediation for any exposed Joomla site using Page Builder CK. The combination of no authentication, remote code execution, critical severity, and KEV status creates high business risk.
Technical view
The issue is CWE-434: unrestricted upload of dangerous file types. The source bundle describes unauthenticated arbitrary file upload leading to full RCE, with CVSS 4.0 score 10.0. The title states Page Builder CK versions before 3.6.0; the affected data lists 1.0-3.6.0, so verify exact vendor guidance.
Likely exposure
Internet-facing Joomla sites with Page Builder CK installed are the primary exposure. Risk is highest where the extension is outdated and reachable without authentication.
Exploitation context
Active exploitation is supported by the CISA Known Exploited Vulnerabilities reference in the source bundle. No exploit mechanics are provided here.
Researcher notes
Evidence is strong for critical unauthenticated upload-to-RCE and known exploitation. Version scope has a minor inconsistency between the title and affected range; validate against the vendor patch advisory before closing findings.
Mitigation direction
- Identify all Joomla sites using Page Builder CK.
- Update Page Builder CK according to joomlack.fr guidance, including the 3.6.0 patch reference.
- If immediate update is impossible, restrict public access until remediated.
- Review servers for unexpected uploaded executable files.
- Back up evidence before cleanup if compromise is suspected.
Validation and detection
- Inventory installed Page Builder CK versions across Joomla sites.
- Compare versions against vendor and CVE guidance.
- Confirm public reachability of affected Joomla instances.
- Review webroot upload directories for suspicious executable content.
- Check web server logs for anomalous unauthenticated upload activity.
- Confirm CISA KEV tracking and internal remediation deadlines.
Public sources used
Michael Williams reviewed this cited source version on .
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-434: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupFile access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-56290 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 10 (4.0)
- Known Exploited
- Yes
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:A/AU:Y/U:Red
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:A/AU:Y/U:Red——JoomlaVulnerability scoring details
Base CVSS 4.0 score
10CriticalVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:A/AU:Y/U:Red
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://www.joomlack.fr/CVE reference, Joomla · product
- https://mysites.guru/blog/pagebuilderck-unauthenticated-file-upload-rce/CVE reference, CISA-ADP · third-party-advisory
- https://forum.joomlack.fr/index.php/page-builder-ck/21627-nouvelle-version-de-pbck-et-joomla-3CVE reference, CISA-ADP · patch
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56290CVE reference, CISA-ADP · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Unrestricted Upload of File with Dangerous Type
Unrestricted Upload of File with Dangerous Type represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.