CVE-2026-81925

What it is

Concrete CMS before 9.5.3 improperly neutralized a user-supplied custom date format when rendering conversation messages, resulting in reflected cross-site scripting. An attacker could execute arbitrary JavaScript in the browser of a user who was tricked into submitting a crafted POST request to the conversation view endpoint. Exploitation was aided by the absence of a CSRF token on the endpoint, which allowed the payload to be delivered through an auto-submitting cross-origin POST without authentication. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account, but needs a user to act. Limited direct impact.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2026-09-15 20:18 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-09-21 17:53 UTC Last updatedMost recent change to the record

Details

Published

2026-09-15 20:18 UTC

Last modified

2026-09-21 17:53 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-79 · Cross-site scripting

Record status

Analyzed

Affected

• Concretecms Concrete Cms < 9.5.3

Attack profile CVSS 4.0 · 2.1

Attack vector

Network

Complexity

Low

Attack requirements

Present

Privileges needed

Low

User interaction

Passive

Confidentiality

Low

Integrity

Low

Availability

None