CVE-2026-105244
Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content
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 value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.
This issue affects Apache log4net: from 1.2.12 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: RemoteSyslogAppender silently deletes non-ASCII content
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 value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.
This issue affects Apache log4net: from 1.2.12 before 3.5.0.
Users are recommended to upgrade to version 3.5.0, which fixes the issue.
- Record
CVE-2026-105244- 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-116
- Updated
- 2026-11-02
EUVDEUVD-2026-93870
5.3
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 value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.
This issue affects Apache log4net: from 1.2.12 before 3.5.0.
Users are recommended to upgrade to version 3.5.0, which fixes the issue.
- Record
EUVD-2026-93870- 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-g956-ph29-3vq5
5.3
Improper Encoding or Escaping of Output vulnerability in the RemoteSyslogAppender of Apache...
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 value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.
This issue affects Apache log4net: from 1.2.12 before 3.5.0.
Users are recommended to upgrade to version 3.5.0, which fixes the issue.
- Record
GHSA-g956-ph29-3vq5- 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-116
- Updated
- 2026-11-02
NVD
5.3
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 value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.
This issue affects Apache log4net: from 1.2.12 before 3.5.0.
Users are recommended to upgrade to version 3.5.0, which fixes the issue.
- Record
CVE-2026-105244- 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-116
- Updated
- 2026-11-02
OSV
5.3
Apache log4net: RemoteSyslogAppender silently deletes non-ASCII content
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 value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected.
This issue affects Apache log4net: from 1.2.12 before 3.5.0.
Users are recommended to upgrade to version 3.5.0, which fixes the issue.
- Record
CVE-2026-105244- 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-116
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-105244
5.3
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 value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected. This issue affects Apache log4net: from 1.2.12 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.
- Record
DEBIAN-CVE-2026-105244- 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-2026-105244
5.3
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 value look identical in the record, for example a user name holding a zero-width space logged as admin. Only applications that use RemoteSyslogAppender are affected. This issue affects Apache log4net: from 1.2.12 before 3.5.0. Users are recommended to upgrade to version 3.5.0, which fixes the issue.
- Record
UBUNTU-CVE-2026-105244- 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-2026-105244 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/77717061b20d4346b6c0ce6b54643d85fb348bc7
lists.apache.org/thread.html/q7649hhdodthoqw8jsjgtnb4m8qfy6d6
openwall.com/lists/oss-security/2026/10/07/19
nvd.nist.gov/vuln/detail/CVE-2026-105244
github.com/advisories/GHSA-g956-ph29-3vq5
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nuget.org/packages
github.com/CVEProject/cvelistV5/tree/main/cves/2026/105xxx/CVE-2026-105244.json
gitbox.apache.org/repos/asf/logging-log4net.git
security-tracker.debian.org/tracker/CVE-2026-105244
ubuntu.com/security/CVE-2026-105244
cve.org/CVERecord?id=CVE-2026-105244
lists.apache.org/thread/q7649hhdodthoqw8jsjgtnb4m8qfy6d6