PT-2026-42544 · Unknown · Concrete Cms

Winston Crooker · CVE-2026-8204 · Published 2026-05-21 · Updated 2026-05-21

Positive Technologies (AI Summary)

CVSS v4.0

6.3

Medium

Base vector

AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Name of the Vulnerable Software and Affected Versions Concrete CMS versions prior to 9.5.1

Description An authorization bypass exists in the Calendar Event Frontend Dialog. This flaw allows for cross-calendar data disclosure, where a public calendar block can be utilized as a pivot point to gain unauthorized access to private calendar data.

Recommendations Update to a version newer than 9.5.0.

Exploit

Fix

IDOR

Weakness Enumeration

CWE-639

Related Identifiers

CVE-2026-8204

GHSA-X2FP-HJ8C-MMXH

Affected Products

Concrete Cms

References · 7

• 🔥 https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/8xxx/CVE-2026-8204.json · Exploit
• https://osv.dev/vulnerability/CVE-2026-8204 · Vendor Advisory
• https://osv.dev/vulnerability/GHSA-x2fp-hj8c-mmxh · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-8204 · Security Note
• https://github.com/concretecms/concretecms · Note
• https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes · Note
• https://t.me/CVEtracker/54550 · Telegram Post