CVE-2026-81910 (GCVE-0-2026-81910)
Vulnerability from cvelistv5 – Published: 2026-09-11 18:20 – Updated: 2026-09-11 19:28- CWE-1336 - Improper neutralization of special elements used in a template engine
| URL | Tags |
|---|---|
| https://documentation.concretecms.org/developers/… | release-notes |
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Concrete CMS | Concrete CMS |
Affected:
9.0.0 , ≤ 9.5.2
(git)
|
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-81910",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-11T19:28:21.654493Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-09-11T19:28:32.382Z",
"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": "tenzai"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003e\u003cspan\u003eConcrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values. Values submitted through the customizer (color channels and other style properties handled by ColorStyle and sibling Style classes such as FontFamilyStyle and ImageStyle) are interpolated into server-compiled LESS source without neutralization of LESS syntax, allowing a user with the Theme Customization permission to inject arbitrary LESS directives. By injecting the @import (inline) directive, an attacker can read arbitrary files on the server and reach internal network resources through PHP stream wrappers. The compiled output, including any disclosed file contents, is written to the site\u0027s publicly served CSS cache, exposing database credentials, private keys, and other application secrets, and enabling server-side request forgery.\u0026nbsp;\u003c/span\u003eThe Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.9 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.\u003c/p\u003e"
}
],
"value": "Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values. Values submitted through the customizer (color channels and other style properties handled by ColorStyle and sibling Style classes such as FontFamilyStyle and ImageStyle) are interpolated into server-compiled LESS source without neutralization of LESS syntax, allowing a user with the Theme Customization permission to inject arbitrary LESS directives. By injecting the @import (inline) directive, an attacker can read arbitrary files on the server and reach internal network resources through PHP stream wrappers. The compiled output, including any disclosed file contents, is written to the site\u0027s publicly served CSS cache, exposing database credentials, private keys, and other application secrets, and enabling server-side request forgery.\u00a0The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.9 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting."
}
],
"impacts": [
{
"capecId": "CAPEC-242",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-242 Code Injection"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"exploitMaturity": "NOT_DEFINED",
"privilegesRequired": "HIGH",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-1336",
"description": "CWE-1336 Improper neutralization of special elements used in a template engine",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-11T18:20:25.958Z",
"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": "3891241",
"defect": [
"HackerOne"
],
"discovery": "EXTERNAL"
},
"title": "Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values",
"x_generator": {
"engine": "Vulnogram 1.0.5"
}
}
},
"cveMetadata": {
"assignerOrgId": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
"assignerShortName": "ConcreteCMS",
"cveId": "CVE-2026-81910",
"datePublished": "2026-09-11T18:20:25.958Z",
"dateReserved": "2026-08-27T18:21:25.200Z",
"dateUpdated": "2026-09-11T19:28:32.382Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-81910",
"date": "2026-11-11",
"epss": "0.00415",
"percentile": "0.3629"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"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"
}
]
}
],
"source": "ff5b8ace-8b95-4078-9743-eac1ca5451de"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*",
"matchCriteriaId": "0B103ED4-9AA0-4776-8FBD-870A5F0A0F92",
"versionEndExcluding": "9.5.3",
"versionStartIncluding": "9.0.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values. Values submitted through the customizer (color channels and other style properties handled by ColorStyle and sibling Style classes such as FontFamilyStyle and ImageStyle) are interpolated into server-compiled LESS source without neutralization of LESS syntax, allowing a user with the Theme Customization permission to inject arbitrary LESS directives. By injecting the @import (inline) directive, an attacker can read arbitrary files on the server and reach internal network resources through PHP stream wrappers. The compiled output, including any disclosed file contents, is written to the site\u0027s publicly served CSS cache, exposing database credentials, private keys, and other application secrets, and enabling server-side request forgery.\u00a0The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.9 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting."
}
],
"id": "CVE-2026-81910",
"lastModified": "2026-09-16T17:40:45.243",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 6.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"version": "3.1"
},
"exploitabilityScore": 2.8,
"impactScore": 3.6,
"source": "nvd@nist.gov",
"type": "Primary"
}
],
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "HIGH",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"source": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-81910",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-11T19:28:21.654493Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-09-11T19:17:46.610",
"references": [
{
"source": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
"tags": [
"Broken Link"
],
"url": "https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes"
}
],
"sourceIdentifier": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-1336"
}
],
"source": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-81910",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-11T19:28:21.654493Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-09-11T19:28:26.783Z",
"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": "tenzai"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003e\u003cspan\u003eConcrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values. Values submitted through the customizer (color channels and other style properties handled by ColorStyle and sibling Style classes such as FontFamilyStyle and ImageStyle) are interpolated into server-compiled LESS source without neutralization of LESS syntax, allowing a user with the Theme Customization permission to inject arbitrary LESS directives. By injecting the @import (inline) directive, an attacker can read arbitrary files on the server and reach internal network resources through PHP stream wrappers. The compiled output, including any disclosed file contents, is written to the site\u0027s publicly served CSS cache, exposing database credentials, private keys, and other application secrets, and enabling server-side request forgery.\u0026nbsp;\u003c/span\u003eThe Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.9 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.\u003c/p\u003e"
}
],
"value": "Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values. Values submitted through the customizer (color channels and other style properties handled by ColorStyle and sibling Style classes such as FontFamilyStyle and ImageStyle) are interpolated into server-compiled LESS source without neutralization of LESS syntax, allowing a user with the Theme Customization permission to inject arbitrary LESS directives. By injecting the @import (inline) directive, an attacker can read arbitrary files on the server and reach internal network resources through PHP stream wrappers. The compiled output, including any disclosed file contents, is written to the site\u0027s publicly served CSS cache, exposing database credentials, private keys, and other application secrets, and enabling server-side request forgery.\u00a0The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.9 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting."
}
],
"impacts": [
{
"capecId": "CAPEC-242",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-242 Code Injection"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"exploitMaturity": "NOT_DEFINED",
"privilegesRequired": "HIGH",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-1336",
"description": "CWE-1336 Improper neutralization of special elements used in a template engine",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-11T18:20:25.958Z",
"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": "3891241",
"defect": [
"HackerOne"
],
"discovery": "EXTERNAL"
},
"title": "Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values",
"x_generator": {
"engine": "Vulnogram 1.0.5"
}
}
},
"cveMetadata": {
"assignerOrgId": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
"assignerShortName": "ConcreteCMS",
"cveId": "CVE-2026-81910",
"datePublished": "2026-09-11T18:20:25.958Z",
"dateReserved": "2026-08-27T18:21:25.200Z",
"dateUpdated": "2026-09-11T19:28:32.382Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.