CriticalCVE-2026-56290

    Joomla Extension - joomlack.fr - Unauthenticated file upload in Page Builder CK extension < 3.6.0 (CVE-2026-56290)

    Published Last modified In CISA KEV since Sources: SingCERT, CVE.org, pwn.watch

    What is affected, what to do

    Joomla Extension - joomlack.fr - Unauthenticated file upload in Page Builder CK extension < 3.6.0 - The Joomla extension Page Builder CK is vulnerable to an unauthenticated arbitrary file upload that allows uploading executable files and leads to full RCE.

    The vulnerability is being actively exploited; treat it as a priority. Update page_builder_ck to version 3.6.0. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • JoomlaCK.fr Page Builder CK extension for Joomla eq 1.0-3.6.0..1.0-3.6.0

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    10.0

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v4

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: SingCERT, CVE.org, pwn.watch

    30.9 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 98.3

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    247.00 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab), CSA/SingCERT How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    10.0 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    10.0
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    30.9 %
    Elevated — model estimates 10-50% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    98.3
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 8 July 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-434, CWE-434

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw is reachable over the network with no authentication and no user interaction, and a single file upload gives the attacker full code execution on the web server. Joomla extension bugs like this are typically mass-scanned and exploited automatically to drop webshells. Attackers then use them for SEO spam, phishing kits, cryptomining or as a foothold into the internal network. This CVE sits among those most likely to be exploited. CISA has not flagged ransomware use, but that does not reduce urgency for internet-facing sites. Treat any internet-exposed Joomla instance running Page Builder CK below 3.6.0 as critical: patch or disable it within 24 hours and run a compromise check. Internal-only instances can follow within your standard critical-patch window.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Find every Joomla site running the Page Builder CK extension (com_pagebuilderck), including staging, campaign and forgotten microsites. Check the version under "System → Manage Extensions" or in administrator/components/com_pagebuilderck/pagebuilderck.xml.
      • Patch: Update Page Builder CK to 3.6.0 or later. NVD lists all versions < 3.6.0 as vulnerable, with the fix in 3.6.0. Because the vendor's affected-range data is inconsistent, install the latest release available from joomlack.fr.
      • If you cannot patch now: Disable or uninstall the extension in the Joomla backend. Alternatively, block unauthenticated front-end access to option=com_pagebuilderck at the web server or WAF.
      • Hunt for prior compromise before patching: Search the webroot for newly created executable files (.php, .phtml, .phar, .php5), especially in upload/media directories such as /images/ and /media/. Example: find /var/www -type f -regex '.*\.\(php\|phtml\|phar\|php[0-9]\)' -newermt "2026-06-01". Patching does not remove an already-planted webshell.
      • If compromise is suspected: Isolate the host and preserve evidence (webroot, access logs, database dump). Then rotate all Joomla admin accounts, the DB password and $secret in configuration.php, and any FTP/SFTP and hosting-panel credentials.
      • Check reporting obligations: NIS2/KRITIS entities must track their reporting clocks (24 h early warning to BSI or the competent national authority) once a significant incident is confirmed.

    2. Runbook step 2

      Mitigation layers

      • WAF/reverse proxy: Block multipart POST requests to index.php carrying option=com_pagebuilderck when no valid Joomla session cookie is present. Also reject uploads with executable or double extensions (shell.php.jpg) across the board. If you run ModSecurity with the OWASP CRS, make sure rule 933110 (PHP file upload) and the 932/941 families are enabled.
      • Web server hardening: Disable PHP execution in all upload directories.
        • Apache: <Directory "/var/www/html/images"> php_admin_flag engine off </Directory> or an .htaccess with <FilesMatch "\.ph(p[0-9]?|tml|ar)$"> Require all denied </FilesMatch>.
        • nginx: location ~* ^/(images|media)/.*\.ph(p|tml|ar)$ { deny all; }
      • Filesystem permissions: Keep the webroot read-only for the PHP runtime user (e.g. www-data). Grant write access only to the cache and upload paths that strictly need it, and keep those non-executable.
      • Runtime hardening: In php.ini, set disable_functions = exec,passthru,shell_exec,system,proc_open,popen and restrict open_basedir to the webroot. This limits what a webshell can do if one lands.
      • Segmentation: Place CMS servers in a DMZ with no direct path to internal networks. Apply egress filtering so the web server can reach only required destinations (update servers, SMTP relay), which kills reverse shells and tool downloads.
      • Lock down /administrator: Restrict the backend path to an IP allowlist or VPN, and enforce 2FA for all administrators.

    3. Runbook step 3

      Detection rules

      • Web access logs: Look for POST requests to option=com_pagebuilderck with no preceding backend login, followed by GET requests to new .php files under /images/ or /media/.
        • SPL: index=web method=POST uri_query="*option=com_pagebuilderck*" | stats count by src_ip, uri_query, status
        • Then correlate with: index=web method=GET uri_path="/images/*.php*"
      • File integrity (auditd/FIM): Watch the upload directory with -w /var/www/html/images -p wa -k joomla_upload. Alert when comm=php-fpm or apache2 creates files with executable extensions. Sysmon for Linux EID 11 (FileCreate) gives you the same signal.
      • EDR process ancestry: Alert on apache2, httpd, php-fpm or nginx spawning sh, bash, curl, wget, python, perl, nc or base64. Sigma shape: ParentImage|endswith: ['/php-fpm','/apache2','/httpd'] AND Image|endswith: ['/sh','/bash','/curl','/wget'].
      • Network telemetry (Zeek/Suricata): Watch for new outbound connections from the web server to unfamiliar hosts or unusual ports. Also flag HTTP responses from /images/*.php containing webshell markers (eval(, base64_decode(, assert().
      • Joomla database: Flag new rows in #__users mapped to the Super Users group (#__user_usergroup_map, group_id 8) outside change windows.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Joomla Extension - joomlack.fr - Unauthenticated file upload in Page Builder CK extension < 3.6.0 - The Joomla extension Page Builder CK is vulnerable to an unauthenticated arbitrary file upload that allows uploading executable files and leads to full RCE.

    Source: CSA/SingCERT, cvelistv5, NVD (NIST), pwn.watch, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    joomlack.frJoomlaCK.fr Page Builder CK extension for Joomla
    • 1.0-3.6.0
    • —
    joomlackpage_builder_ck
    • < 3.6.0
    • 3.6.0

    Vendors and products

    Weakness classes (CWE)

    • CWE-434Unrestricted Upload of File with Dangerous Type

      Base

      The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.

      Entry at MITRE CWE-434

    • CWE-434Unrestricted Upload of File with Dangerous Type

      Base

      The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.

      Entry at MITRE CWE-434

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    CSA/SingCERTActive Exploitation of Critical Vulnerabilities in Joomla Extensions (opens in a new tab)CSA/SingCERTactively exploited
    PoC-in-GitHub (nomi-sec)CVE-2026-56290_PoC (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)CVE-2026-56290 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)PageBuilderCK-CVE-2026-56290-Exploit (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)pbck-exploit (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • joomlack.frProduct, Product
    • mysites.gurublog/pagebuilderck-unauthenticated-file-upload-rceThird-party advisory, Exploit, Third-party advisory
    • forum.joomlack.frindex.php/page-builder-ck/21627-nouvelle-version-de-pbck-et-joo…Patch, Issue tracking, Patch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56290government-resource, US government resource
    • pwn.watchpwn.watch: Joomlack Page Builder: Joomlack Page Builder Improper Access Control Vulnerabilitypwn-watch
    • joomlack.frJoomlack Page Builder — CVE-2026-56290pwn-watch
    • NVD (NIST)NVD: CVE-2026-56290pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedJoomla

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://www.joomlack.fr/
      Referenceremoved
      https://www.joomlack.fr/
      —
      Reference typeremoved
      https://www.joomlack.fr/ Types: Product
      —

      Source identifier: security@joomla.org

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: yes

      Show 11 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://forum.joomlack.fr/index.php/page-builder-ck/21627-nouvelle-version-de-pbck-et-joomla-3
      Referenceadded
      —
      https://mysites.guru/blog/pagebuilderck-unauthenticated-file-upload-rce/
      Referenceadded
      —
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56290
      Referenceremoved
      https://forum.joomlack.fr/index.php/page-builder-ck/21627-nouvelle-version-de-pbck-et-joomla-3
      —
      Referenceremoved
      https://mysites.guru/blog/pagebuilderck-unauthenticated-file-upload-rce/
      —
      Referenceremoved
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56290
      —
      Reference typeremoved
      https://forum.joomlack.fr/index.php/page-builder-ck/21627-nouvelle-version-de-pbck-et-joomla-3 Types: Issue Tracking, Patch
      —
      Reference typeremoved
      https://mysites.guru/blog/pagebuilderck-unauthenticated-file-upload-rce/ Types: Exploit, Third Party Advisory
      —
      Reference typeremoved
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-56290 Types: US Government Resource
      —
      SSVC assessmentremoved
      {"id":"CVE-2026-56290","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-06-30T00:00:00+00:00"}
      —
      SSVC assessmentadded
      —
      {"id":"CVE-2026-56290","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-07-08T03:56:32.575114Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    3. NVD analysis modifiedNVD

    4. Record modifiedJoomla

      Description added or changed

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionchanged
      The Joomla extension Page Builder CK is vulnerable to an unauthenticated arbitrary file upload that allows uploading executable files and leads to full RCE.
      Joomla Extension - joomlack.fr - Unauthenticated file upload in Page Builder CK extension < 3.6.0 - The Joomla extension Page Builder CK is vulnerable to an unauthenticated arbitrary file upload that allows uploading executable files and leads to full RCE.

      Source identifier: security@joomla.org

    5. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: yes

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentchanged
      {"id":"CVE-2026-56290","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-07-07T17:45:15.592601Z"}
      {"id":"CVE-2026-56290","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-06-30T00:00:00+00:00"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Show 2 older changes

    1. Record modifiedJoomla

      Weakness type: CWE-434

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-434
      Weakness type (CWE)removed
      CWE-284
      —

      Source identifier: security@joomla.org

    2. Initial analysis by NVDNVD

      Newly listed as affected:
      • JoomlaCK.fr Page Builder CK extension for Joomla (through 3.6.0)

      CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

      Weakness type: CWE-434

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
      Weakness type (CWE)added
      —
      CWE-434
      Product configurationadded
      —
      OR *cpe:2.3:a:joomlack:page_builder_ck:*:*:*:*:*:joomla!:*:* versions up to (including) 3.6.0
      Reference typeadded
      —
      Joomla! Project: https://www.joomlack.fr/ Types: Product
      Reference typeadded
      —
      CISA-ADP: https://forum.joomlack.fr/index.php/page-builder-ck/21627-nouvelle-version-de-pbck-et-joomla-3 Types: Issue Tracking, Patch
      Reference typeadded
      —
      CISA-ADP: https://mysites.guru/blog/pagebuilderck-unauthenticated-file-upload-rce/ Types: Exploit, Third Party Advisory

      Source identifier: nvd@nist.gov

    One NVD translation into another language is hidden.

    Linked advisories

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    Badge preview for CVE-2026-56290
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-56290"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-56290.svg?lang=en" alt="CVE-2026-56290 – NEOSEC Intel" height="20"></a>