CVE-2026-81900

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Source
https://cve.org/CVERecord?id=CVE-2026-81900
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81900.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-81900
Published
2026-09-14T22:07:58Z
Modified
2026-09-18T03:48:30Z
Severity
  • 7.3 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N CVSS Calculator
Summary
Concrete CMS before 9.5.3 is vulnerable to Stored XSS in the YouTube block (vWidth/vHeight)
Details

Concrete CMS before 9.5.3 applied only trim() to the YouTube block's stored width and height values and printed them into iframe HTML attributes without escaping or integer casting, resulting in stored cross-site scripting. A user with edit_block permission could inject an event handler that executed script for visitors rendering the page, acting with administrative privileges where the victim was an administrator. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks sh4d0byss for reporting.

Database specific 
{
    "cna_assigner": "ConcreteCMS",
    "cwe_ids": [
        "CWE-79"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81900.json"
}
References

Affected packages

Git / github.com/concretecms/concretecms

Affected ranges

Type
GIT
Repo
https://github.com/concretecms/concretecms
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
9379c29cb26a1054208b37507b6869811aa75a32
Database specific
Show details 
{
    "cpe": "cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*",
    "extracted_events": [
        {
            "introduced": "5.0.0"
        },
        {
            "last_affected": "9.5.2"
        },
        {
            "introduced": "0"
        },
        {
            "fixed": "9.5.3"
        }
    ],
    "source": [
        "AFFECTED_FIELD",
        "CPE_RANGE"
    ]
}

Affected versions

5.*
5.7.0
5.7.0.1
5.7.0.3
5.7.0.4
5.7.1
5.7.2
5.7.2.1
5.7.3
5.7.3.1
5.7.4.1
5.7.5.2
5.7.5.5
5.7.5.6
5.7.5.7
8.*
8.1.0
8.2.0
8.2.0RC2
8.2.1
8.3.1
8.4.1
9.*
9.3.0
9.3.1
9.3.2
9.3.3
9.3.4
9.3.5
9.3.6
9.3.7
9.4.0
9.4.0RC1
9.4.0RC2
9.4.1
9.4.2
9.4.3
9.4.4
9.5.0
9.5.0RC1
9.5.0RC2
9.5.1
9.5.2

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81900.json"