CriticalFix available
undertow — security advisory
A flaw was found in the Undertow HTTP server core, which is used in WildFly, JBoss EAP, and other Java applications. The Undertow library fails to properly validate the Host header in incoming HTTP requests.As a result, requests containing malformed or malicious Host headers are processed without rejection, enabling attackers to poison caches, perform internal network scans, or hijack user sessions.
- Products
- undertow
- Affected versions
- 1.3.11-1, 1.3.16-1, 1.3.4-1, 1.3.5-1, 1.3.7-1, 1.4.20-1, 1.4.21-1, 1.4.22-1, 1.4.23-1, 1.4.23-2build1, 1.4.23-3, 2.0.23-1, 2.0.27-1, 2.0.28-1, 2.0.29-1, 2.2.12-1, 2.2.13-1, 2.2.14-1, 2.2.16-1, 2.2.8-1, 2.3.18-1, 2.3.18-2, 2.3.20-1, 2.3.8-2
- Fixed versions
- 1.3.16-1ubuntu0.1~esm1, 1.4.23-3ubuntu0.1~esm1, 2.0.29-1ubuntu0.1~esm1, 2.2.16-1ubuntu0.1~esm1, 2.3.20-1ubuntu1, 2.3.8-2ubuntu0.1~esm1
- CVEs
- CVE-2025-12543
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 01:30 UTC · Revision 1
Source evidence
A flaw was found in the Undertow HTTP server core, which is used in WildFly, JBoss EAP, and other Java applications. The Undertow library fails to properly validate the Host header in incoming HTTP requests.As a result, requests containing malformed or malicious Host headers are processed without rejection, enabling attackers to poison caches, perform internal network scans, or hijack user sessions.
osv:UBUNTU-CVE-2025-12543
undertow
Fixed versions: 1.3.16-1ubuntu0.1~esm1
undertow
Fixed versions: 1.4.23-3ubuntu0.1~esm1
undertow
Fixed versions: 2.0.29-1ubuntu0.1~esm1
undertow
Fixed versions: 2.2.16-1ubuntu0.1~esm1
undertow
Fixed versions: 2.3.8-2ubuntu0.1~esm1
undertow
Fixed versions: Not specified
undertow
Fixed versions: 2.3.20-1ubuntu1
undertow
Fixed versions: 2.3.20-1ubuntu1
Complete source record
{
"id": "92241b9e8bc85eefa5d7d39c32535431fb99fb494d96e467b8b6290436f947ed",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2025-12543",
"method": "structured",
"payload": {
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"title": "UBUNTU-CVE-2025-12543",
"summary": "A flaw was found in the Undertow HTTP server core, which is used in WildFly, JBoss EAP, and other Java applications. The Undertow library fails to properly validate the Host header in incoming HTTP requests.As a result, requests containing malformed or malicious Host headers are processed without rejection, enabling attackers to poison caches, perform internal network scans, or hijack user sessions.",
"evidence": "osv:UBUNTU-CVE-2025-12543",
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{
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"severity": "critical",
"structured": {
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"aliases": [
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"metrics": [
{
"type": "CVSS_V3",
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{
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{
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"package": {
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"binary_name": "libundertow-java",
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}
}
],
"modified": "2026-10-17T12:57:00.504423758Z",
"provider": "osv",
"upstream": [
"CVE-2025-12543"
],
"references": [
"https://ubuntu.com/security/CVE-2025-12543",
"https://www.cve.org/CVERecord?id=CVE-2025-12543",
"https://access.redhat.com/security/cve/CVE-2025-12543",
"https://bugzilla.redhat.com/show_bug.cgi?id=2408784",
"https://github.com/undertow-io/undertow/pull/1857",
"https://github.com/undertow-io/undertow/pull/1882",
"https://github.com/undertow-io/undertow/pull/1860",
"https://github.com/undertow-io/undertow/pull/1894",
"https://ubuntu.com/security/notices/USN-8144-1"
]
},
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{
"value": "CVE-2025-12543",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 356625,
"published_at": "2026-01-07T17:15:00+00:00"
}