CVE detail
CVE-2026-40021
Apache 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.
Buzz score
Why this CVE is surfacing
This all-time snapshot uses the same composite formula as Trending across a 30-year evidence window, rather than a current rolling window.
Buzz score components · mention 19.5 · diversity 13.0 · KEV 0.0 · OTX 0.0 · PoC 0.0
Why it matters now
Mention timeline
- Total mentions
- 0
- within the 30d window
- Peak daily
- 0
- highest bucket
Evidence
Source links by recency
6 source links · newest first
- http://www.openwall.com/lists/oss-security/2026/04/10/11www.openwall.com
No excerpt available.
Exploitwww.openwall.comApr 10, 2026, 4:16 PM - https://logging.apache.org/security.html#CVE-2026-40021logging.apache.org
No excerpt available.
Vendor Advisorylogging.apache.orgApr 10, 2026, 4:16 PM - https://logging.apache.org/log4net/manual/configuration/layouts.htmllogging.apache.org
No excerpt available.
Vendor Advisorylogging.apache.orgApr 10, 2026, 4:16 PM - https://logging.apache.org/cyclonedx/vdr.xmllogging.apache.org
No excerpt available.
Vendor Advisorylogging.apache.orgApr 10, 2026, 4:16 PM - https://lists.apache.org/thread/q8otftjswhk69n3kxslqg7cobr0x4st7lists.apache.org
No excerpt available.
Vendor Advisorylists.apache.orgApr 10, 2026, 4:16 PM No excerpt available.
Exploitgithub.comApr 10, 2026, 4:16 PM
Exploit code
Public exploit repository references
Public PoC repositories are third-party, potentially unsafe artifacts. Treat their code as untrusted and use it only on authorized systems in an isolated, least-privilege environment. cvebuzz does not execute the code or verify that an exploit works.
0 repository references · best confidence N/A · max 0 stars
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