High
modsecurity — security advisory
ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Libmodsecurity is one component of the ModSecurity v3 project. A segmentation fault occurs when a rule using the t:hexDecode transformation inspects a query string parameter containing a single character. An attacker can exploit this to crash worker processes, causing a denial of service. Service resumes once the attack stops as worker processes recover from the segfault. All versions before 3.0.15 of libModSecurity3 are affected. This has been patched in version 3.0.15.
- Products
- modsecurity
- Affected versions
- 3.0.10-1, 3.0.11-1, 3.0.12-1, 3.0.12-1.1build1, 3.0.12-1.1build2, 3.0.13-1, 3.0.14-1, 3.0.14-1build1, 3.0.14-1build2, 3.0.15-1, 3.0.16-1, 3.0.3-1, 3.0.4-1, 3.0.4-1build1, 3.0.4-2, 3.0.6-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-30923
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:06 UTC · Revision 1
Source evidence
ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Libmodsecurity is one component of the ModSecurity v3 project. A segmentation fault occurs when a rule using the t:hexDecode transformation inspects a query string parameter containing a single character. An attacker can exploit this to crash worker processes, causing a denial of service. Service resumes once the attack stops as worker processes recover from the segfault. All versions before 3.0.15 of libModSecurity3 are affected. This has been patched in version 3.0.15.
osv:UBUNTU-CVE-2026-30923
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
Complete source record
{
"id": "2f34c94cde4a0e31a099082043e88c2356600a7bd6977a4ad048152b9070ad10",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-30923",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-30923",
"summary": "ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Libmodsecurity is one component of the ModSecurity v3 project. A segmentation fault occurs when a rule using the t:hexDecode transformation inspects a query string parameter containing a single character. An attacker can exploit this to crash worker processes, causing a denial of service. Service resumes once the attack stops as worker processes recover from the segfault. All versions before 3.0.15 of libModSecurity3 are affected. This has been patched in version 3.0.15.",
"evidence": "osv:UBUNTU-CVE-2026-30923",
"products": [
{
"name": {
"value": "modsecurity",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.3-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.0.4-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.0.4-1build1",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
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"evidence": "/affected/1/package/name"
},
"prerequisites": [],
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"affected_versions": [
{
"value": "3.0.4-2",
"evidence": "/affected/1/versions"
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{
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"evidence": "/affected/1/versions"
}
]
},
{
"name": {
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"evidence": "/affected/2/package/name"
},
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"affected_versions": [
{
"value": "3.0.10-1",
"evidence": "/affected/2/versions"
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{
"value": "3.0.11-1",
"evidence": "/affected/2/versions"
},
{
"value": "3.0.12-1",
"evidence": "/affected/2/versions"
},
{
"value": "3.0.12-1.1build1",
"evidence": "/affected/2/versions"
},
{
"value": "3.0.12-1.1build2",
"evidence": "/affected/2/versions"
}
]
},
{
"name": {
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"evidence": "/affected/3/package/name"
},
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"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.13-1",
"evidence": "/affected/3/versions"
},
{
"value": "3.0.14-1",
"evidence": "/affected/3/versions"
},
{
"value": "3.0.14-1build1",
"evidence": "/affected/3/versions"
}
]
},
{
"name": {
"value": "modsecurity",
"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.14-1build2",
"evidence": "/affected/4/versions"
},
{
"value": "3.0.15-1",
"evidence": "/affected/4/versions"
},
{
"value": "3.0.16-1",
"evidence": "/affected/4/versions"
}
]
},
{
"name": {
"value": "modsecurity",
"evidence": "/affected/5/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.14-1build1",
"evidence": "/affected/5/versions"
},
{
"value": "3.0.14-1build2",
"evidence": "/affected/5/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "UBUNTU-CVE-2026-30923",
"aliases": [
"UBUNTU-CVE-2026-30923"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
},
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "modsecurity",
"purl": "pkg:deb/ubuntu/modsecurity?arch=source&distro=focal",
"ecosystem": "Ubuntu:20.04:LTS"
},
"versions": [
"3.0.3-1",
"3.0.4-1",
"3.0.4-1build1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-30923.json"
},
"ecosystem_specific": {
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{
"binary_name": "libmodsecurity3",
"binary_version": "3.0.4-1build1"
}
]
}
},
{
"ranges": [
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}
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],
"package": {
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"ecosystem": "Ubuntu:22.04:LTS"
},
"versions": [
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"3.0.6-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-30923.json"
},
"ecosystem_specific": {
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{
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}
]
}
},
{
"ranges": [
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]
}
],
"package": {
"name": "modsecurity",
"purl": "pkg:deb/ubuntu/modsecurity?arch=source&distro=noble",
"ecosystem": "Ubuntu:24.04:LTS"
},
"versions": [
"3.0.10-1",
"3.0.11-1",
"3.0.12-1",
"3.0.12-1.1build1",
"3.0.12-1.1build2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-30923.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmodsecurity3t64",
"binary_version": "3.0.12-1.1build2"
}
]
}
},
{
"ranges": [
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"package": {
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"ecosystem": "Ubuntu:25.10"
},
"versions": [
"3.0.13-1",
"3.0.14-1",
"3.0.14-1build1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-30923.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmodsecurity3t64",
"binary_version": "3.0.14-1build1"
}
]
}
},
{
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"package": {
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"ecosystem": "Ubuntu:26.10"
},
"versions": [
"3.0.14-1build2",
"3.0.15-1",
"3.0.16-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-30923.json"
},
"ecosystem_specific": {
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{
"binary_name": "libmodsecurity3t64",
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}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
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}
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}
],
"package": {
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"purl": "pkg:deb/ubuntu/modsecurity?arch=source&distro=resolute",
"ecosystem": "Ubuntu:26.04:LTS"
},
"versions": [
"3.0.14-1build1",
"3.0.14-1build2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-30923.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmodsecurity3t64",
"binary_version": "3.0.14-1build2"
}
]
}
}
],
"modified": "2026-10-17T12:58:08.314995958Z",
"provider": "osv",
"upstream": [
"CVE-2026-30923"
],
"references": [
"https://ubuntu.com/security/CVE-2026-30923",
"https://www.cve.org/CVERecord?id=CVE-2026-30923",
"https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-qrjc-3jpc-3h2g"
]
},
"related_cves": [
{
"value": "CVE-2026-30923",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 358206,
"published_at": "2026-05-05T19:16:00+00:00"
}