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TI-2026-68919 Aliases CVE-2026-105239GHSA-wf3f-44xg-jxj3

NUL character truncates EventLogAppender records in Apache log4net

Priority LOW 32CWE-158Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

Apache log4net from 1.2.9 before 3.5.0 has a NUL character weakness (CWE-158) in its EventLogAppender. A NUL character in logged content ends the Windows Event Log record there, so the rest of the record, including exception text and trailing fields, is not stored. A party whose data reaches a log message can hide the rest of that record. Only applications on Windows that use EventLogAppender are affected.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

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 message could hide the rest of that record. Only applications on Windows that use EventLogAppender are affected. This issue affects Apache log4net: from 1.2.9 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00823 57th percentileScored 2026-11-07
Fix Fixed Apache log4net (Apache Software Foundation): 3.5.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
ApacheApache log4net1.2.9 to before 3.5.03.5.0Patch availableCNA
  • Apache log4net VendorApache Affected 1.2.9 to before 3.5.0 Fixed in 3.5.0 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:apache:log4net:*:*:*:*:*:*:*:*1.2.9 to before 3.5.0VulnerableApache
  • cpe:2.3:a:apache:log4net:*:*:*:*:*:*:*:* Versions 1.2.9 to before 3.5.0 Vulnerable ·Apache

Remediation

Upgrade Apache log4net to version 3.5.0, which fixes the issue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

  • Fix · CNA Apache log4net (Apache Software Foundation) Fixed in 3.5.0

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    Apache log4net 3.5.0

    6 records Highest priority Priority LOW 6 LOW

    Other records, highest priority first

    • TI-2026-68924 RemoteSyslogAppender in Apache log4net silently drops non-ASCII textPriority LOW 32
    • TI-2026-68923 Apache log4net EventLogAppender silently discards oversize recordsPriority LOW 32
    • TI-2026-68922 Log4net drops log events when ASP.NET request validation failsPriority LOW 32
    Show all 6 records →

Timeline

  1. 2026-10-06 Threatist record created from CVE-2026-105239
  2. 2026-10-07 Alias added: GHSA-wf3f-44xg-jxj3
  3. 2026-10-11 EPSS moved to the 50th–90th percentile

References

Patch 2

Advisory 2

  • TI-2018-01190 XML external entity injection in Apache log4net CVSS 3.1CRITICAL 9.8
  • TI-2026-68924 RemoteSyslogAppender in Apache log4net silently drops non-ASCII text CVSS 3.1MEDIUM 5.3
  • TI-2026-68923 Apache log4net EventLogAppender silently discards oversize records CVSS 3.1MEDIUM 5.3
  • TI-2026-68922 Log4net drops log events when ASP.NET request validation fails CVSS 3.1MEDIUM 5.3
  • TI-2026-68921 Unencodable content drops a whole batch in Apache log4net appender CVSS 3.1MEDIUM 5.3
  • TI-2026-68920 NUL character truncates log records in Apache log4net debug output CVSS 3.1MEDIUM 5.3
See all 8 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences