CVE-2026-40023
Publication date 10 April 2026
Last updated 10 July 2026
Ubuntu priority
Description
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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| log4cxx | 26.04 LTS resolute |
Needs evaluation
|
| 24.04 LTS noble |
Needs evaluation
|
|
| 22.04 LTS jammy |
Needs evaluation
|
|
| 20.04 LTS focal |
Needs evaluation
|
|
| 18.04 LTS bionic |
Needs evaluation
|
|
| 16.04 LTS xenial |
Needs evaluation
|
|
| 14.04 LTS trusty |
Needs evaluation
|
Severity score breakdown
CVSS version:
Base score
6.3 · Medium
Vector: 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
Base score
5.3 · Medium
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
References
Other references
- 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
- http://www.openwall.com/lists/oss-security/2026/04/10/12