CVE-2026-105239
Apache log4net: NUL character truncates EventLogAppender records
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
5.3
Apache log4net: NUL character truncates EventLogAppender records
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.
- Record
CVE-2026-105239- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-158
- Updated
- 2026-11-02
EUVDEUVD-2026-93863
5.3
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.
- Record
EUVD-2026-93863- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-wf3f-44xg-jxj3
5.3
Improper Neutralization of Null Byte or NUL Character vulnerability in the EventLogAppender of...
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.
- Record
GHSA-wf3f-44xg-jxj3- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-158
- Updated
- 2026-11-02
NVD
5.3
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.
- Record
CVE-2026-105239- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-158
- Updated
- 2026-11-02
OSV
5.3
Apache log4net: NUL character truncates EventLogAppender records
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.
- Record
CVE-2026-105239- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-158
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-105239
5.3
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.
- Record
DEBIAN-CVE-2026-105239- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-105239
5.3
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.
- Record
UBUNTU-CVE-2026-105239- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
log4netDebian:13 |
All versions, plus listed versions 1.2.10+dfsg-101.2.10+dfsg-9 |
None known |
log4netDebian:14 |
All versions, plus listed versions 1.2.10+dfsg-101.2.10+dfsg-9 |
None known |
log4netUbuntu:16.04:LTS |
All versions, plus listed versions 1.2.10+dfsg-61.2.10+dfsg-71.2.10+dfsg-7ubuntu0.16.04.1 |
None known |
log4netUbuntu:18.04:LTS |
All versions, plus listed versions 1.2.10+dfsg-71.2.10+dfsg-7ubuntu0.18.04.1 |
None known |
log4netUbuntu:20.04:LTS |
All versions, plus listed versions 1.2.10+dfsg-71.2.10+dfsg-7ubuntu0.20.04.1 |
None known |
log4netUbuntu:22.04:LTS |
All versions, plus listed versions 1.2.10+dfsg-8 |
None known |
log4netUbuntu:24.04:LTS |
All versions, plus listed versions 1.2.10+dfsg-81.2.10+dfsg-9 |
None known |
log4netUbuntu:26.10 |
All versions, plus listed versions 1.2.10+dfsg-9build11.2.10+dfsg-10 |
None known |
log4netUbuntu:26.04:LTS |
All versions, plus listed versions 1.2.10+dfsg-91.2.10+dfsg-9build1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-105239 is a medium vulnerability (CVSS 5.3) in Apache Log4net, published October 6, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.82%, the 57th percentile. No source names a fixed version.
References
github.com/apache/logging-log4net/pull/315
github.com/apache/logging-log4net/commit/dc5855a0720c91590fd7a81d729ea01fdd69e000
lists.apache.org/thread.html/9fx1qo5hc0tg8ym0t6p9gt1zpb2qlxpq
openwall.com/lists/oss-security/2026/10/07/14
nvd.nist.gov/vuln/detail/CVE-2026-105239
github.com/advisories/GHSA-wf3f-44xg-jxj3
Show 7 moreShow less
nuget.org/packages
github.com/CVEProject/cvelistV5/tree/main/cves/2026/105xxx/CVE-2026-105239.json
gitbox.apache.org/repos/asf/logging-log4net.git
security-tracker.debian.org/tracker/CVE-2026-105239
ubuntu.com/security/CVE-2026-105239
cve.org/CVERecord?id=CVE-2026-105239
lists.apache.org/thread/9fx1qo5hc0tg8ym0t6p9gt1zpb2qlxpq