Apache Software Foundation Apache Log4Net vulnerabilities

CVE-2026-105242 [MEDIUM] CWE-755 CVE-2026-105242: Improper Handling of Exceptional Conditions vulnerability in the aspnet-request pattern converter of Improper Handling of Exceptional Conditions vulnerability in the aspnet-request pattern converter of Apache log4net. Reading request parameters triggers ASP.NET request validation, so a request carrying content such as markup made the layout throw and the appender discarded the whole event. A sender could suppress the log record of their own requ

CVE-2026-40021 [MEDIUM] CWE-116 CVE-2026-40021: Apache Log4net's XmlLayout https://logging.apache.org/log4net/manual/configuration/layouts.html#lay 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

CVE-2026-105241 [MEDIUM] CWE-176 CVE-2026-105241: Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net. Improper Handling of Unicode Encoding vulnerability in the SmtpPickupDirAppender of Apache log4net. Content that the mail file writer cannot encode, such as an unpaired UTF-16 surrogate, made the write throw. Every buffered event in the batch was discarded, not only the one carrying the content, and a truncated mail could be left in the pickup dir

CVE-2026-105239 [MEDIUM] CWE-158 CVE-2026-105239: Improper Neutralization of Null Byte or NUL Character vulnerability in the EventLogAppender of Apach Improper Neutralization of Null Byte or NUL Character vulnerability in the EventLogAppender of Apache log4net. A NUL character in logged content ended the Windows Event Log record at that point, so everything the layout rendered after it, including exception text and trailing fields, was silently not stored. A party whose data reaches a log messa

CVE-2026-105244 [MEDIUM] CWE-116 CVE-2026-105244: Improper Encoding or Escaping of Output vulnerability in the RemoteSyslogAppender of Apache log4net. Improper Encoding or Escaping of Output vulnerability in the RemoteSyslogAppender of Apache log4net. Every character outside visible ASCII and space was removed from the record instead of being escaped, so non-ASCII text and control characters such as tabs disappeared without notice. A party whose data reaches a log message could make a distinct

CVE-2026-105243 [MEDIUM] CWE-778 CVE-2026-105243: Insufficient Logging vulnerability in the EventLogAppender of Apache log4net. Long messages were tr Insufficient Logging vulnerability in the EventLogAppender of Apache log4net. Long messages were truncated to a fixed size that exceeds what the Windows Event Log accepts once the log and source names are counted, and the event log then stored nothing and reported nothing. A party whose data reaches a log message could suppress the whole record by

CVE-2026-105240 [MEDIUM] CWE-158 CVE-2026-105240: Improper Neutralization of Null Byte or NUL Character vulnerability in the OutputDebugStringAppender Improper Neutralization of Null Byte or NUL Character vulnerability in the OutputDebugStringAppender of Apache log4net. A NUL character in logged content ended the debug output record at that point, so everything the layout rendered after it, including exception text and trailing fields, was silently lost. A party whose data reaches a log message