How severe is CVE-2026-105243?

CVE-2026-105243 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2026-105243 being actively exploited?

It is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no EPSS exploit-prediction score is available yet.

How do I fix CVE-2026-105243?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-105243 published?

CVE-2026-105243 was published on 2026-10-06.

CVE-2026-105243

CVE-2026-105243 is a medium-severity vulnerability with a CVSS 3.x base score of 5.3. The underlying weakness is classified as CWE-778.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-778
Published: 2026-10-06
Last modified: 2026-10-06

Description

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 making it long enough. 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.

Frequently asked questions

What is CVE-2026-105243?: 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 making it long enough. 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.
How severe is CVE-2026-105243?: CVE-2026-105243 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2026-105243 being actively exploited?: It is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no EPSS exploit-prediction score is available yet.
How do I fix CVE-2026-105243?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-105243 published?: CVE-2026-105243 was published on 2026-10-06.

References

Other CWE-778 vulnerabilities

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CVE-2026-76208 — High (CVSS 8.2): phpMyFAQ versions 3.1.0 through 4.1.6 contain an authentication bypass vulnerability in AuthLdap::create(). When LDAP…
CVE-2021-43419 — High (CVSS 7.5): An Information Disclosure vulnerability exists in Opay Mobile application 1.5.1.26 and maybe be higher in the logcat…
CVE-2019-7613 — High (CVSS 7.5): Winlogbeat versions before 5.6.16 and 6.6.2 had an insufficient logging flaw. An attacker able to inject certain…
CVE-2026-66816 — Medium (CVSS 6.5): Insufficient logging in SQL Server allows an authorized attacker to bypass a security feature over a network.
CVE-2019-19277 — Medium (CVSS 6.5): A vulnerability has been identified in SIPORT MP (All versions < 3.1.4). Vulnerable versions of the device allow the…

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