---
id: CVE-2026-81905
title: >-
  Concrete CMS below 9.5.3 stores user validation hashes for multiple purposes
  (email/registration validation, password reset, and persistent login) in a
  single table with a type column, but the redemption path resolves a hash by
  value alo…
summary: >-
  Concrete CMS below 9.5.3 stores user validation hashes for multiple purposes
  (email/registration validation, password reset, and persistent login) in a
  single table with a type column, but the redemption path resolves a hash by
  value alo…
severity: medium
cvss: 6.3
cvssVector: 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N'
cwe:
  - CWE-640
  - CWE-863
vendor: Concrete CMS
product: Concrete CMS
affected:
  - concrete_cms >= 5.0.0 <= 9.5.2
published: '2026-09-11'
updated: '2026-09-11'
sourceUpdated: '2026-09-11T15:17:05.890'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-81905'
references:
  - url: >-
      https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes
    label: ff5b8ace-8b95-4078-9743-eac1ca5451de
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-11T14:28:56.366688Z'
cvssSource: cna
ingestedAt: '2026-09-13T03:57:14.979Z'
epss: 0.00356
epssPercentile: 0.26677
---

## Overview

Concrete CMS below 9.5.3 stores user validation hashes for multiple purposes (email/registration validation, password reset, and persistent login) in a single table with a type column, but the redemption path resolves a hash by value alone and does not verify its type. As a result, a hash issued for one purpose can be redeemed for another: a long-lived registration hash (60-day expiry) can be submitted to the password-change endpoint to set a new password on the target account, and a password-reset hash can be submitted to the email-validation endpoint to activate an account. Exploitation requires the attacker to first obtain a valid hash through a separate channel (for example email interception, log exposure, or SSRF against an internal mail relay), so the flaw amplifies the impact of any hash disclosure rather than creating a standalone entry point. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.