Open Redirect in Cotonti
CVE-2026-100523
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.
Vulnerability class: Open Redirect
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.002 (8.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 8th percentile — 8.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
Weakness classification (CWE)
References
- github.com/Cotonti/Cotonti (product)
- github.com/Cotonti/Cotonti/blob/1.0.0/message.php (technical-description)
- github.com/Cotonti/Cotonti/blob/1.0.0/system/common.php (technical-description)
- github.com/Cotonti/Cotonti/issues/1907 (issue-tracking)
- github.com/Cotonti/Cotonti/pull/1908 (issue-tracking, patch)
- VulnCheck Advisory: Cotonti through 1.0.0 Open Redirect via message.php redirect parameter (third-party-advisory)
Frequently asked questions
- What is CVE-2026-100523?
- CVE-2026-100523 is a medium-severity vulnerability in Cotonti, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2026-09-26.
- How severe is CVE-2026-100523?
- Medium severity. CVSS v3 base score is 6.1 out of 10.