---
id: CVE-2026-100523
title: >-
  Cotonti through 1.0.0 contains an open redirect vulnerability in message.php
  that base64-decodes the redirect parameter without domain validation
summary: >-
  Cotonti through 1.0.0 contains an open redirect vulnerability in message.php
  that base64-decodes the redirect parameter without domain validation.
  Unauthenticated attackers can craft malicious links with encoded external URLs
  to redirect…
severity: medium
cvss: 6.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'
cwe:
  - CWE-601
vendor: Cotonti
product: Cotonti
affected:
  - Cotonti <= 1.0.0
published: '2026-09-26'
updated: '2026-10-05'
sourceUpdated: '2026-10-05T15:17:10.117'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100523'
references:
  - url: 'https://github.com/Cotonti/Cotonti'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/Cotonti/Cotonti/blob/1.0.0/message.php'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/Cotonti/Cotonti/blob/1.0.0/system/common.php'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/Cotonti/Cotonti/issues/1907'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/Cotonti/Cotonti/pull/1908'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/cotonti-through-1.0.0-open-redirect-via-message-php-redirect-parameter
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-05T14:01:31.542603Z'
epss: 0.00188
epssPercentile: 0.08285
ingestedAt: '2026-09-26T01:24:36.887Z'
---

## Overview

Cotonti through 1.0.0 contains an open redirect vulnerability in message.php that base64-decodes the redirect parameter without domain validation. Unauthenticated attackers can craft malicious links with encoded external URLs to redirect users to arbitrary sites via meta refresh tags for phishing attacks.

## Remediation

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