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    CVE-2026-81913

    Concrete CMS versions 9.5.0 through 9.5.2 are vulnerable to Open Redirect via the rcURL parameter. An attacker can craft a single link on the site's own domain that sends a user to an arbitrary external site immediately after authentication, facilitating phishing and credential theft. The same handling is present in the registration flow, giving a second entry point on sites with registration enabled. Concrete CMS versions prior to 9.5.0 do not include the rcURL parameter or this allowlist and are not affected. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.3 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Michal M. for reporting.

    Published:Sep 11, 2026
    Last Modified:Sep 12, 2026
    EPS:Sep 11, 2026
    EPSS Score:0.0052
    CVSS Score:5.3

    Affected Products

    Vendor
    Concretecms
    Product
    Concrete Cms

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-178 Cross-Site Flashing

    Related CVEs

    CVE-2026-81918 (CVSS 4.8) — Concrete CMS below 9.5.3 is vulnerable to Stored XSS via the Date Format field in the Page Attribute Display b…
    CVE-2026-81917 (CVSS 5.1) — Concrete CMS below 9.5.3 does not apply HTML output escaping to the file description and tags fields when rend…
    CVE-2026-68535 (CVSS 5.1) — Concrete CMS Area API's block-create endpoint in versions 9.2.0 to 9.5.2 did not invoke the block type control…
    CVE-2026-81915 (CVSS 5.1) — Concrete CMS below 9.5.3 does not perform an object-level authorization check when a Page Type was updated. Th…
    CVE-2026-68526 (CVSS 5.3) — Concrete CMS before 9.5.3 did not validate an anti-CSRF token in the Calendar event duplicate dialog controlle…
    CVE-2026-81912 (CVSS 5.7) — Concrete CMS before 9.5.3 is vulnerable to Cross-Site Request Forgery in the Move Multiple Groups feature. The…
    CVE-2026-81911 (CVSS 5.8) — Concrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot dialog. The custom_slot …
    CVE-2026-81910 (CVSS 5.9) — Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Un…
    CVE-2026-68528 (CVSS 6) — Concrete CMS RSS Displayer block below version 9.5.3 rendered remote feed item titles without HTML escaping, …
    CVE-2026-81908 (CVSS 6) — Concrete CMS 9.2.0 to 9.5.2 contain a missing authorization vulnerability in the REST API Groups list endpoint…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    CVE-2026-81913 — Concretecms (Medium 5.3) | CVE-DB