CVE-2026-105243

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreHIGH confidence

Score 5.3 from GitHub Security Advisory published 2026-10-06. A secondary CVSS source baseline 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.3Exploit: None knownExposed services: Not assessed

The CVE record names the fixed release — apply it.

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.

CVSS v3
5.3
EG Score
5.3MEDIUMhigh confidence
EG Risk
39
EG Risk 39/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity53% × 45%
Exploitation0% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: The CVE record names the fixed release. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
24th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

The CVE record names the fixed release. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

October 6, 2026

Last Modified

October 9, 2026

Advisory Details (3)

Auto-updated Oct 6, 2026
Fix named in the CVE record. Sources: github_pr, github_commit.
generic

Pony Mail

https://lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rp
github_commit

commit 28fbfb25678c (apache/logging-log4net)

Fix landed in apache/logging-log4net commit 28fbfb25678c — awaiting tagged release

https://github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed
github_pr

Escaping special characters in multiple appenders

Fix merged in apache/logging-log4net PR #315 on 2026-09-04 — awaiting tagged release

https://github.com/apache/logging-log4net/pull/315

Vendor Advisories for CVE-2026-105243(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 19× in last 7d / 19× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-09 20:06 UTCEPSS rescore
  2. 2026-10-09 15:34 UTCEG score recompute
  3. 2026-10-09 15:34 UTCGHSA enrichment
  4. 2026-10-08 17:11 UTCEPSS rescore
  5. 2026-10-08 15:33 UTCEG score recompute
  6. 2026-10-08 15:33 UTCGHSA enrichment
  7. 2026-10-07 23:47 UTCEPSS rescore
  8. 2026-10-07 15:31 UTCEG score recompute
  9. 2026-10-07 15:31 UTCGHSA enrichment
  10. 2026-10-07 15:02 UTCEG score recompute
  11. 2026-10-07 15:02 UTCGHSA enrichment
  12. 2026-10-07 13:46 UTCGHSA enrichment
  13. 2026-10-07 07:28 UTCEG score recompute
  14. 2026-10-07 07:28 UTCGHSA enrichment
  15. 2026-10-07 06:23 UTCEG score recompute
  16. 2026-10-07 06:23 UTCGHSA enrichment
  17. 2026-10-06 20:32 UTCEG score recompute
  18. 2026-10-06 19:58 UTCEG score recompute
  19. 2026-10-06 19:56 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-105243?
CVE-2026-105243 is a medium vulnerability published on October 6, 2026. 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…
When was CVE-2026-105243 disclosed?
CVE-2026-105243 was first published on October 6, 2026, with the most recent update on October 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-105243 actively exploited?
CVE-2026-105243 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (24th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-105243?
CVE-2026-105243 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-105243?
The CVE record for CVE-2026-105243 names the fix: "Users are recommended to upgrade to version 3.5.0, which fixes the issue." The vendor advisories EchelonGraph has for CVE-2026-105243 are linked in the Vendor Advisories panel on this page.

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