Grav before 2.0.14 Stored XSS via Invalid UTF-8 Byte
Grav before 2.0.14 contains a stored cross-site scripting vulnerability in the Security::detectXss() function (system/src/Grav/Common/Security.php). All XSS detection patterns use the PCRE /u (UTF-8) modifier, so a single invalid UTF-8 byte anywhere in page content causes preg_match() to return false for every pattern, silently bypassing the save-time XSS safety gate (Validation::checkSafety()). An authenticated attacker with page-edit permissions (without the security.xss_whitelist privilege) can store malicious JavaScript that executes in the browser of a visitor who views the affected page.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-75834
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 5 Nov 2026, 03:05 UTC · Revision 1
Source evidence
Grav before 2.0.14 Stored XSS via Invalid UTF-8 Byte
core-osv · Original sourcePublished 18 Aug 2026, 11:19 UTC
Grav before 2.0.14 contains a stored cross-site scripting vulnerability in the Security::detectXss() function (system/src/Grav/Common/Security.php). All XSS detection patterns use the PCRE /u (UTF-8) modifier, so a single invalid UTF-8 byte anywhere in page content causes preg_match() to return false for every pattern, silently bypassing the save-time XSS safety gate (Validation::checkSafety()). An authenticated attacker with page-edit permissions (without the security.xss_whitelist privilege) can store malicious JavaScript that executes in the browser of a visitor who views the affected page.
osv:CVE-2026-75834
Complete source record
{
"id": "7bc87dfb7e050bebb32e65f66567e096c03c8066258fbdcc3c3ad19b3d31441e",
"url": "https://osv.dev/vulnerability/CVE-2026-75834",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Grav before 2.0.14 Stored XSS via Invalid UTF-8 Byte",
"summary": "Grav before 2.0.14 contains a stored cross-site scripting vulnerability in the Security::detectXss() function (system/src/Grav/Common/Security.php). All XSS detection patterns use the PCRE /u (UTF-8) modifier, so a single invalid UTF-8 byte anywhere in page content causes preg_match() to return false for every pattern, silently bypassing the save-time XSS safety gate (Validation::checkSafety()). An authenticated attacker with page-edit permissions (without the security.xss_whitelist privilege) can store malicious JavaScript that executes in the browser of a visitor who views the affected page.",
"evidence": "osv:CVE-2026-75834",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-75834",
"aliases": [
"CVE-2026-75834",
"GHSA-q2j8-x8hf-63ch"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/getgrav/grav",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "5192316f5bf0f033636f43561829d7fc13a4ab64"
}
],
"database_specific": {
"extracted_events": [
{
"range": [
{
"introduced": "0"
},
{
"fixed": "2.0.14"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
},
{
"range": [
{
"introduced": "0"
},
{
"fixed": "2.0.14"
}
],
"source": "DESCRIPTION"
}
]
}
}
],
"versions": [
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"0.9.19",
"0.9.18",
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"0.9.5",
"0.9.4",
"0.9.3",
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],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-75834.json"
}
}
],
"modified": "2026-10-28T02:30:41.972939228Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/75xxx/CVE-2026-75834.json",
"https://github.com/getgrav/grav/security/advisories/GHSA-q2j8-x8hf-63ch",
"https://nvd.nist.gov/vuln/detail/CVE-2026-75834",
"https://www.vulncheck.com/advisories/grav-before-stored-xss-via-invalid-utf-8-byte"
],
"provider_metadata": {
"cwe_ids": [
"CWE-79"
],
"cna_assigner": "VulnCheck",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/75xxx/CVE-2026-75834.json"
}
},
"related_cves": [
{
"value": "CVE-2026-75834",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 509689,
"published_at": "2026-08-18T11:19:45.094+00:00"
}