Medium
log4cxx — security advisory
Apache Log4cxx's XMLLayout https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html , in versions before 1.7.0, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets in log messages, NDC, and MDC property keys and values, producing invalid XML output. Conforming XML parsers must reject such documents with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records. An attacker who can influence logged data can exploit this to suppress individual log records, impairing audit trails and detection of malicious activity. Users are advised to upgrade to Apache Log4cxx 1.7.0, which fixes this issue.
- Products
- log4cxx
- Affected versions
- 0.10.0-1.2ubuntu3, 0.10.0-10ubuntu1, 0.10.0-12ubuntu1, 0.10.0-13ubuntu1, 0.10.0-13ubuntu2, 0.10.0-15ubuntu1, 0.10.0-15ubuntu2, 0.10.0-9ubuntu1, 0.10.0-9ubuntu2, 0.11.0-2ubuntu1, 0.11.0-3ubuntu2, 0.12.1-4, 1.1.0-1, 1.1.0-1build1, 1.1.0-1build2, 1.1.0-1build3, 1.3.1-1, 1.4.0-1, 1.5.0-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-40023
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:10 UTC · Revision 1
Source evidence
Apache Log4cxx's XMLLayout https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html , in versions before 1.7.0, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets in log messages, NDC, and MDC property keys and values, producing invalid XML output. Conforming XML parsers must reject such documents with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records. An attacker who can influence logged data can exploit this to suppress individual log records, impairing audit trails and detection of malicious activity. Users are advised to upgrade to Apache Log4cxx 1.7.0, which fixes this issue.
osv:UBUNTU-CVE-2026-40023
log4cxx
Fixed versions: Not specified
log4cxx
Fixed versions: Not specified
log4cxx
Fixed versions: Not specified
log4cxx
Fixed versions: Not specified
log4cxx
Fixed versions: Not specified
log4cxx
Fixed versions: Not specified
log4cxx
Fixed versions: Not specified
log4cxx
Fixed versions: Not specified
log4cxx
Fixed versions: Not specified
Complete source record
{
"id": "08fe04577f2e216c04f80c38d3b55942e3dd1b4fe31c7474e8d1b6bdfc986bc1",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-40023",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-40023",
"summary": "Apache Log4cxx's XMLLayout https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html , in versions before 1.7.0, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets in log messages, NDC, and MDC property keys and values, producing invalid XML output. Conforming XML parsers must reject such documents with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records. An attacker who can influence logged data can exploit this to suppress individual log records, impairing audit trails and detection of malicious activity. Users are advised to upgrade to Apache Log4cxx 1.7.0, which fixes this issue.",
"evidence": "osv:UBUNTU-CVE-2026-40023",
"products": [
{
"name": {
"value": "log4cxx",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "0.10.0-1.2ubuntu3",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "log4cxx",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "0.10.0-9ubuntu1",
"evidence": "/affected/1/versions"
},
{
"value": "0.10.0-9ubuntu2",
"evidence": "/affected/1/versions"
},
{
"value": "0.10.0-10ubuntu1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "log4cxx",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "0.10.0-12ubuntu1",
"evidence": "/affected/2/versions"
},
{
"value": "0.10.0-13ubuntu1",
"evidence": "/affected/2/versions"
},
{
"value": "0.10.0-13ubuntu2",
"evidence": "/affected/2/versions"
}
]
},
{
"name": {
"value": "log4cxx",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "0.10.0-15ubuntu1",
"evidence": "/affected/3/versions"
},
{
"value": "0.10.0-15ubuntu2",
"evidence": "/affected/3/versions"
}
]
},
{
"name": {
"value": "log4cxx",
"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "0.11.0-2ubuntu1",
"evidence": "/affected/4/versions"
},
{
"value": "0.11.0-3ubuntu2",
"evidence": "/affected/4/versions"
},
{
"value": "0.12.1-4",
"evidence": "/affected/4/versions"
}
]
},
{
"name": {
"value": "log4cxx",
"evidence": "/affected/5/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.1.0-1",
"evidence": "/affected/5/versions"
},
{
"value": "1.1.0-1build1",
"evidence": "/affected/5/versions"
},
{
"value": "1.1.0-1build2",
"evidence": "/affected/5/versions"
},
{
"value": "1.1.0-1build3",
"evidence": "/affected/5/versions"
}
]
},
{
"name": {
"value": "log4cxx",
"evidence": "/affected/6/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.3.1-1",
"evidence": "/affected/6/versions"
},
{
"value": "1.4.0-1",
"evidence": "/affected/6/versions"
}
]
},
{
"name": {
"value": "log4cxx",
"evidence": "/affected/7/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.5.0-1",
"evidence": "/affected/7/versions"
}
]
},
{
"name": {
"value": "log4cxx",
"evidence": "/affected/8/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.4.0-1",
"evidence": "/affected/8/versions"
},
{
"value": "1.5.0-1",
"evidence": "/affected/8/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "UBUNTU-CVE-2026-40023",
"aliases": [
"UBUNTU-CVE-2026-40023"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N"
},
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "log4cxx",
"purl": "pkg:deb/ubuntu/log4cxx?arch=source&distro=trusty",
"ecosystem": "Ubuntu:14.04:LTS"
},
"versions": [
"0.10.0-1.2ubuntu3"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40023.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liblog4cxx10",
"binary_version": "0.10.0-1.2ubuntu3"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "log4cxx",
"purl": "pkg:deb/ubuntu/log4cxx?arch=source&distro=xenial",
"ecosystem": "Ubuntu:16.04:LTS"
},
"versions": [
"0.10.0-9ubuntu1",
"0.10.0-9ubuntu2",
"0.10.0-10ubuntu1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40023.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liblog4cxx10v5",
"binary_version": "0.10.0-10ubuntu1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "log4cxx",
"purl": "pkg:deb/ubuntu/log4cxx?arch=source&distro=bionic",
"ecosystem": "Ubuntu:18.04:LTS"
},
"versions": [
"0.10.0-12ubuntu1",
"0.10.0-13ubuntu1",
"0.10.0-13ubuntu2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40023.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liblog4cxx10v5",
"binary_version": "0.10.0-13ubuntu2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "log4cxx",
"purl": "pkg:deb/ubuntu/log4cxx?arch=source&distro=focal",
"ecosystem": "Ubuntu:20.04:LTS"
},
"versions": [
"0.10.0-15ubuntu1",
"0.10.0-15ubuntu2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40023.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liblog4cxx10v5",
"binary_version": "0.10.0-15ubuntu2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "log4cxx",
"purl": "pkg:deb/ubuntu/log4cxx?arch=source&distro=jammy",
"ecosystem": "Ubuntu:22.04:LTS"
},
"versions": [
"0.11.0-2ubuntu1",
"0.11.0-3ubuntu2",
"0.12.1-4"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40023.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liblog4cxx12",
"binary_version": "0.12.1-4"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "log4cxx",
"purl": "pkg:deb/ubuntu/log4cxx?arch=source&distro=noble",
"ecosystem": "Ubuntu:24.04:LTS"
},
"versions": [
"1.1.0-1",
"1.1.0-1build1",
"1.1.0-1build2",
"1.1.0-1build3"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40023.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liblog4cxx15",
"binary_version": "1.1.0-1build3"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "log4cxx",
"purl": "pkg:deb/ubuntu/log4cxx?arch=source&distro=questing",
"ecosystem": "Ubuntu:25.10"
},
"versions": [
"1.3.1-1",
"1.4.0-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40023.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liblog4cxx15",
"binary_version": "1.4.0-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "log4cxx",
"purl": "pkg:deb/ubuntu/log4cxx?arch=source&distro=stonking",
"ecosystem": "Ubuntu:26.10"
},
"versions": [
"1.5.0-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40023.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liblog4cxx15",
"binary_version": "1.5.0-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "log4cxx",
"purl": "pkg:deb/ubuntu/log4cxx?arch=source&distro=resolute",
"ecosystem": "Ubuntu:26.04:LTS"
},
"versions": [
"1.4.0-1",
"1.5.0-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40023.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "liblog4cxx15",
"binary_version": "1.5.0-1"
}
]
}
}
],
"modified": "2026-10-17T12:58:13.880353188Z",
"provider": "osv",
"upstream": [
"CVE-2026-40023"
],
"references": [
"https://ubuntu.com/security/CVE-2026-40023",
"https://www.cve.org/CVERecord?id=CVE-2026-40023",
"https://github.com/apache/logging-log4cxx/pull/609",
"https://logging.apache.org/security.html#CVE-2026-40023",
"https://lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b",
"https://logging.apache.org/cyclonedx/vdr.xml",
"https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html"
]
},
"related_cves": [
{
"value": "CVE-2026-40023",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 358390,
"published_at": "2026-04-10T16:16:00+00:00"
}