CVE-2026-81911 (GCVE-0-2026-81911)
Vulnerability from cvelistv5
Published
2026-09-11 19:24
Modified
2026-09-11 19:33
Severity ?
VLAI Severity ?
EPSS score ?
CWE
- CWE-79 - Cross-site Scripting (XSS) - Stored
Summary
Concrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot dialog. The custom_slot save_template endpoint authorizes the request only against the target board instance (canEditBoardContents()) and then persists the client-supplied selectedTemplateOption[collection] verbatim, rather than rebuilding the content object collection server-side and verifying that each item belongs to the authorized board's data pool. A user with permission to edit the contents of at least one board instance can therefore store a forged summary object whose description field carries a JavaScript-bearing HTML payload. The default summary template renders the description field without output encoding, so the payload executes in the browser of any user who views the affected board slot, including anonymous front-end visitors and dashboard users who preview the resulting rule or block. This can enable session or action takeover and escalation toward an administrator. Concrete CMS versions below 9 do not include the Boards feature and are not affected. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.8 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks riodrwn for reporting.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Concrete CMS | Concrete CMS |
Version: 9.0.0 |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-81911",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-11T19:32:11.209005Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-09-11T19:33:33.148Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://github.com/concretecms/concretecms",
"defaultStatus": "unaffected",
"product": "Concrete CMS",
"repo": "https://github.com/concretecms/concretecms",
"vendor": "Concrete CMS",
"versions": [
{
"lessThanOrEqual": "9.5.2",
"status": "affected",
"version": "9.0.0",
"versionType": "git"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "riodrwn"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003e\u003cspan\u003eConcrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot dialog. The custom_slot save_template endpoint authorizes the request only against the target board instance (canEditBoardContents()) and then persists the client-supplied selectedTemplateOption[collection] verbatim, rather than rebuilding the content object collection server-side and verifying that each item belongs to the authorized board\u0027s data pool. A user with permission to edit the contents of at least one board instance can therefore store a forged summary object whose description field carries a JavaScript-bearing HTML payload. The default summary template renders the description field without output encoding, so the payload executes in the browser of any user who views the affected board slot, including anonymous front-end visitors and dashboard users who preview the resulting rule or block. This can enable session or action takeover and escalation toward an administrator. Concrete CMS versions below 9 do not include the Boards feature and are not affected.\u0026nbsp;\u003c/span\u003eThe Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.8 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks riodrwn for reporting.\u003c/p\u003e"
}
],
"value": "Concrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot dialog. The custom_slot save_template endpoint authorizes the request only against the target board instance (canEditBoardContents()) and then persists the client-supplied selectedTemplateOption[collection] verbatim, rather than rebuilding the content object collection server-side and verifying that each item belongs to the authorized board\u0027s data pool. A user with permission to edit the contents of at least one board instance can therefore store a forged summary object whose description field carries a JavaScript-bearing HTML payload. The default summary template renders the description field without output encoding, so the payload executes in the browser of any user who views the affected board slot, including anonymous front-end visitors and dashboard users who preview the resulting rule or block. This can enable session or action takeover and escalation toward an administrator. Concrete CMS versions below 9 do not include the Boards feature and are not affected.\u00a0The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.8 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks riodrwn for reporting."
}
],
"impacts": [
{
"capecId": "CAPEC-592",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-592 Stored XSS"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 5.8,
"baseSeverity": "MEDIUM",
"exploitMaturity": "NOT_DEFINED",
"privilegesRequired": "HIGH",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "PASSIVE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "LOW",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "LOW",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-79",
"description": "CWE-79 Cross-site Scripting (XSS) - Stored",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-11T19:24:05.585Z",
"orgId": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
"shortName": "ConcreteCMS"
},
"references": [
{
"tags": [
"release-notes"
],
"url": "https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes"
}
],
"source": {
"advisory": "3809840",
"defect": [
"HackerOne"
],
"discovery": "EXTERNAL"
},
"title": "Concrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot save_template via Unescaped Summary Description",
"x_generator": {
"engine": "Vulnogram 1.0.5"
}
}
},
"cveMetadata": {
"assignerOrgId": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
"assignerShortName": "ConcreteCMS",
"cveId": "CVE-2026-81911",
"datePublished": "2026-09-11T19:24:05.585Z",
"dateReserved": "2026-08-27T18:21:25.200Z",
"dateUpdated": "2026-09-11T19:33:33.148Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"vulnrichment": {
"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-81911\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-09-11T19:32:11.209005Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-09-11T19:33:26.571Z\"}}], \"cna\": {\"title\": \"Concrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot save_template via Unescaped Summary Description\", \"source\": {\"defect\": [\"HackerOne\"], \"advisory\": \"3809840\", \"discovery\": \"EXTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"riodrwn\"}], \"impacts\": [{\"capecId\": \"CAPEC-592\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"CAPEC-592 Stored XSS\"}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 5.8, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N\", \"exploitMaturity\": \"NOT_DEFINED\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"PASSIVE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"HIGH\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"LOW\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"LOW\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"HIGH\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"repo\": \"https://github.com/concretecms/concretecms\", \"vendor\": \"Concrete CMS\", \"product\": \"Concrete CMS\", \"versions\": [{\"status\": \"affected\", \"version\": \"9.0.0\", \"versionType\": \"git\", \"lessThanOrEqual\": \"9.5.2\"}], \"collectionURL\": \"https://github.com/concretecms/concretecms\", \"defaultStatus\": \"unaffected\"}], \"references\": [{\"url\": \"https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes\", \"tags\": [\"release-notes\"]}], \"x_generator\": {\"engine\": \"Vulnogram 1.0.5\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"Concrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot dialog. The custom_slot save_template endpoint authorizes the request only against the target board instance (canEditBoardContents()) and then persists the client-supplied selectedTemplateOption[collection] verbatim, rather than rebuilding the content object collection server-side and verifying that each item belongs to the authorized board\u0027s data pool. A user with permission to edit the contents of at least one board instance can therefore store a forged summary object whose description field carries a JavaScript-bearing HTML payload. The default summary template renders the description field without output encoding, so the payload executes in the browser of any user who views the affected board slot, including anonymous front-end visitors and dashboard users who preview the resulting rule or block. This can enable session or action takeover and escalation toward an administrator. Concrete CMS versions below 9 do not include the Boards feature and are not affected.\\u00a0The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.8 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks riodrwn for reporting.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003e\u003cspan\u003eConcrete CMS versions 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Board Custom Slot dialog. The custom_slot save_template endpoint authorizes the request only against the target board instance (canEditBoardContents()) and then persists the client-supplied selectedTemplateOption[collection] verbatim, rather than rebuilding the content object collection server-side and verifying that each item belongs to the authorized board\u0027s data pool. A user with permission to edit the contents of at least one board instance can therefore store a forged summary object whose description field carries a JavaScript-bearing HTML payload. The default summary template renders the description field without output encoding, so the payload executes in the browser of any user who views the affected board slot, including anonymous front-end visitors and dashboard users who preview the resulting rule or block. This can enable session or action takeover and escalation toward an administrator. Concrete CMS versions below 9 do not include the Boards feature and are not affected.\u0026nbsp;\u003c/span\u003eThe Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.8 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks riodrwn for reporting.\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-79\", \"description\": \"CWE-79 Cross-site Scripting (XSS) - Stored\"}]}], \"providerMetadata\": {\"orgId\": \"ff5b8ace-8b95-4078-9743-eac1ca5451de\", \"shortName\": \"ConcreteCMS\", \"dateUpdated\": \"2026-09-11T19:24:05.585Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-81911\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-09-11T19:33:33.148Z\", \"dateReserved\": \"2026-08-27T18:21:25.200Z\", \"assignerOrgId\": \"ff5b8ace-8b95-4078-9743-eac1ca5451de\", \"datePublished\": \"2026-09-11T19:24:05.585Z\", \"assignerShortName\": \"ConcreteCMS\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
Loading…
Loading…