CVE Feed

    Dashboard / CVE / CVE-2026-81906

    CVE-2026-81906

    Concrete CMS OAuth callback login path prior to version 9.5.3 did not check whether an account was active or email-validated before establishing a session. A deactivated or unvalidated user with an existing OAuth binding could complete authentication and receive a session that was fully authenticated for the callback response, with the login recorded and login events dispatched. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.

    Published:Sep 10, 2026
    Last Modified:Sep 11, 2026
    EPS:Sep 10, 2026
    EPSS Score:0.00339
    CVSS Score:6.3

    Affected Products

    Vendor
    Concretecms
    Product
    Concrete Cms

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-127 Directory Indexing
    CAPEC-665 Exploitation of Thunderbolt Protection Flaws

    Related CVEs

    CVE-2026-18120 (CVSS 6.3) — Concrete CMS before 9.5.3 exposed a legacy Express entry search endpoint that returned entry result JSON witho…
    CVE-2026-85387 (CVSS 2) — Concrete CMS before 9.5.4 re-authorized OAuth REST API requests from the bearer token alone and did not re-che…
    CVE-2026-87031 (CVSS 2.1) — n Concrete CMS 9.2.0 through 9.5.3, the REST API user creation endpoint (POST /ccm/api/1.0/users, the add() me…
    CVE-2026-87028 (CVSS 5.3) — Concrete CMS 9 through 9.5.3 did not confirm that a board InstanceItem submitted to the custom-slot preview en…
    CVE-2026-85386 (CVSS 7.3) — Concrete CMS before 9.5.4 did not sanitize XML and XSLT documents uploaded through a public Form Block file-up…
    CVE-2026-85385 (CVSS 7.7) — Concrete CMS below 9.5.4 did not validate the user timezone value (uTimezone) on write and rendered it without…
    CVE-2026-81927 (CVSS 1.8) — Concrete CMS before 9.5.3 contained a stored cross-site scripting vulnerability in SVG file handling. When SVG…
    CVE-2026-18426 (CVSS 2) — Concrete CMS 9.0.0 through 9.5.2 did not enforce a block-level edit-permission check on the Express Form block…
    CVE-2026-81926 (CVSS 2) — Concrete CMS 9.4.0 through 9.5.2 did not escape colliding page paths before rendering them in the location pan…
    CVE-2026-81925 (CVSS 2.1) — Concrete CMS before 9.5.3 improperly neutralized a user-supplied custom date format when rendering conversatio…

    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