CVE record · CVE-2026-40023

Apache Log4cxx, Apache Log4cxx (Conan), Apache Log4cxx (Brew): Silent log event loss in XMLLayout due to unescaped XML 1.0 forbidden characters

CVSS 6.3 MediumEPSS 0.0052 · 44th percentile

Published by the CVE Program (CNA: apache) at 10 Apr 2026, 15:45 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
Apache Software Foundation	Apache Log4cxx	affected before 1.7.0 semver Other versions: unaffected
Apache Software Foundation	Apache Log4cxx (Conan) Package name: log4cxx https://conan.io/center pkg:conan/log4cxx	affected before 1.7.0 semver Other versions: unaffected
Apache Software Foundation	Apache Log4cxx (Brew) Package name: log4cxx https://brew.sh/	affected before 1.7.0 semver Other versions: unaffected

Identifiers: CVE-2026-40023
CNA: apache
Weakness (CWE): CWE-116
Tags: Apache Software Foundation Apache Log4cxx
Apache Software Foundation Apache Log4cxx (Conan)
Apache Software Foundation Apache Log4cxx (Brew)
CWE-116
Published: 10 Apr 2026
Updated: 10 Apr 2026

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
6.3	Medium	4.0	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	CNA (apache)

CISA KEV Not listed.
EPSS 0.0052, the 44th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 10 Apr 2026. New records show when each source confirmed them.

Sources

References from the CNA

github.com/apache/logging-log4cxx/pull/609 patch
logging.apache.org/security.html#CVE-2026-40023 vendor-advisory
logging.apache.org/cyclonedx/vdr.xml vendor-advisory
logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html related
lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b vendor-advisory

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.