CVE-2026-40021 Detail
Received
This CVE record has recently been published to the CVE List and has been included within the NVD dataset. DescriptionApache Log4net's XmlLayout https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list and XmlLayoutSchemaLog4J https://logging.apache.org/log4net/manual/configuration/layouts.html#layout-list , in versions before 3.3.0, fail to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets in MDC property keys and values, as well as the identity field that may carry attacker-influenced data. This causes an exception during serialization and the silent loss of the affected log event. An attacker who can influence any of these fields can exploit this to suppress individual log records, impairing audit trails and detection of malicious activity. Users are advised to upgrade to Apache Log4net 3.3.0, which fixes this issue. Metrics
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CVSS 4.0 Severity and Vector Strings:
CNA: Apache Software Foundation
CVSS-B 6.3 MEDIUM
Vector: 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
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Weakness Enumeration
Quick InfoCVE Dictionary Entry:CVE-2026-40021 NVD Published Date: 04/10/2026 NVD Last Modified: 04/10/2026 Source: Apache Software Foundation |
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