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.
References
| Link | Resource |
|---|---|
| https://github.com/apache/logging-log4cxx/pull/609 | Issue Tracking Patch |
| https://lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b | Mailing List Vendor Advisory |
| https://logging.apache.org/cyclonedx/vdr.xml | Product |
| https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html | Product |
| https://logging.apache.org/security.html#CVE-2026-40023 | Vendor Advisory |
| http://www.openwall.com/lists/oss-security/2026/04/10/12 | Mailing List Third Party Advisory |
Configurations
History
21 Apr 2026, 14:49
| Type | Values Removed | Values Added |
|---|---|---|
| References | () https://github.com/apache/logging-log4cxx/pull/609 - Issue Tracking, Patch | |
| References | () https://lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b - Mailing List, Vendor Advisory | |
| References | () https://logging.apache.org/cyclonedx/vdr.xml - Product | |
| References | () https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html - Product | |
| References | () https://logging.apache.org/security.html#CVE-2026-40023 - Vendor Advisory | |
| References | () http://www.openwall.com/lists/oss-security/2026/04/10/12 - Mailing List, Third Party Advisory | |
| First Time |
Apache log4cxx
Apache |
|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 5.3 |
| CPE | cpe:2.3:a:apache:log4cxx:*:*:*:*:*:*:*:* |
10 Apr 2026, 17:17
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
10 Apr 2026, 16:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-04-10 16:16
Updated : 2026-04-21 14:49
NVD link : CVE-2026-40023
Mitre link : CVE-2026-40023
CVE.ORG link : CVE-2026-40023
JSON object : View
Products Affected
apache
- log4cxx
CWE
CWE-116
Improper Encoding or Escaping of Output