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CVE-2026-81925VulnerabilityPublished Updated

Concrete CMS before 9.5.3 improperly neutralized a user-supplied custom date format when rendering conversation

Source GCVE Database

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Not known to be exploited · CVSS 6.1 Medium.

Data as of 31 Oct 2026, 20:20 UTC

CVSS 3.1 base score
6.1Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 19% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 15 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.

What to do

AI-suggested

Until an official fix is available, users should exercise caution when interacting with conversation messages and avoid submitting untrusted POST requests. The absence of a CSRF token on the endpoint suggests that adding CSRF protection would mitigate the issue.

Description

Concrete CMS versions prior to 9.5.3 contain a reflected cross-site scripting (XSS) vulnerability due to improper neutralization of user-supplied custom date formats in conversation message rendering. This flaw allows attackers to execute arbitrary JavaScript in the browsers of users who submit crafted POST requests to the conversation view endpoint. The vulnerability is exacerbated by the lack of a CSRF token on this endpoint, enabling cross-origin POST requests without authentication. The Concrete CMS security team assigned this issue a low severity rating with a CVSS v4.0 score of 2.1.

References

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