Advisory severityMedium6.3Apache Software Foundation

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.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-40023 Source published Apr 10, 2026Source updated Jun 17, 2026

VulniPulse record published Jul 11, 2026

CVE-2026-40023

Affected products & platforms

Apache Software FoundationUnclassified

Open source advisory

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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.

Affected versions

1.7.0

Official advisory · high-confidence parse· fetched 3 months ago·verify at source

Fixed versions

1.7.0

Official advisory · high-confidence parse· fetched 3 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 3 months ago·verify at source

Sources

Official and corroborating records used to build this advisory.

NVD discovery recordNVD
Independent discovery and scoring cross-reference. Vendor remediation guidance takes precedence. Discovered from the machine-readable feed https://services.nvd.nist.gov/rest/json/cves/2.0; this link opens the NVD record for CVE-2026-40023 instead of the raw feed document.
NIST National Vulnerability Database

Cross-references

Validate CVE metadata against the authoritative registries.

CVE-2026-40023NVD CVE.org MITRE

Official resources

ASF Security — reporting & CVE process
Official documentation
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Apache project downloads (fixed releases)
Official documentation
Official ASF download tree — fetch the fixed release named in this advisory from the project's directory.

Discussion(0)

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