Advisory severityMedium5.3Apache Software Foundation Updated

Medium [CVE-2026-105243] Insufficient Logging vulnerability in the EventLogAppender of Apache log4net

This medium-severity Apache Software Foundation advisory covers CVE-2026-105243; related products: Apache log4net.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-105243 Source published Oct 6, 2026Source updated Oct 7, 2026

VulniPulse record published Oct 6, 2026Record updated Oct 7, 2026

CVE-2026-105243

Monitor future Apache Software Foundation CVEs from your phone.

Choose a whole vendor or a precise platform, then receive matching security advisories by phone notification, email, or both. Coverage follows 32 official vendor sources and 160+ reviewed platform categories.

Matching phone alertsOptional email delivery

Get CVE alerts See app features

Summary

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.

Affected versions

1.2.9 before 3.5.0

Official advisory · high-confidence parse· fetched 1 day ago·verify at source

Fixed versions

3.5.0

Official advisory · high-confidence parse· fetched 1 day ago·verify at source

Mitigation checklist

Recommended fix / mitigation

Users are recommended to upgrade to version 3.5.0, which fixes the issue.

Official advisory · high-confidence parse· fetched 1 day ago·verify at source

Sources

Official and corroborating records used to build this advisory.

Official vendor advisoryofficial
Official advisory page fetched and parsed; accepted detail fields are attributed to this page.
Apache Software Foundation
CVE.org CNA recordCVE.org
Independent CNA record used for near-real-time discovery and missed-CVE reconciliation. Discovered from the machine-readable feed https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/delta.json; this link opens the CVE.org record for CVE-2026-105243 instead of the raw feed document.
CVE Program

Cross-references

Validate CVE metadata against the authoritative registries.

CVE-2026-105243NVD CVE.org MITRE

Official resources

ASF Security — reporting & CVE process
Official documentation
The Apache Software Foundation's official security page: how ASF CVEs are published and where each project's advisories live.
Apache project downloads (fixed releases)
Official documentation
Official ASF download tree — fetch the fixed release named in this advisory from the project's directory.

Discussion(0)

No comments yet. Share field notes, upgrade gotchas, or questions — verify against the vendor advisory before acting on community advice.