CVE-2026-40023

medium Apache
CVSS v3 Base Score
5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS Score
0.2%
Exploitation probability in 30 days
Top 64% most likely to be exploited
Attack Characteristics
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Published: April 10, 2026 (33 days ago)
Last Modified: April 21, 2026
Vendor: Apache
Source: NVD

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.

CWE

CWE-116

Affected Products

apache log4cxx

References

🔗 github.com 🔗 lists.apache.org 🔗 logging.apache.org 🔗 logging.apache.org 🔗 logging.apache.org