Medium [CVE-2026-40023] Apache Log4cxx's XMLLayout https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html , in versions before…
This medium-severity Apache Software Foundation advisory covers CVE-2026-40023 affecting Apache Log4cxx.
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Summary
Apache Log4cxx's XMLLayout, in versions before 1.7.0, fails to sanitize characters forbidden by the XML 1.0 specification 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.
- 1.7.0
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation
Upgrade to a fixed release: 1.7.0. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
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