VULNERABILITY INTELLIGENCE

CVE-2026-40023

CVSS score5.3 MEDIUM

EPSS probability0.50%

CISA KEVNot currently listed

Published2026-04-10

Last modified2026-10-26

CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

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.

Weakness classification

security@apache.org: CWE-116

Primary references

security@apache.org — Issue Tracking, Patch
security@apache.org — Mailing List, Vendor Advisory
security@apache.org — Product
security@apache.org — Product
security@apache.org — Vendor Advisory
af854a3a-2127-422b-91ae-364da2661108 — Mailing List, Third Party Advisory