CVE-2026-105240

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.

Improper Neutralization of Null Byte or NUL Character vulnerability in the OutputDebugStringAppender of Apache log4net.

A NUL character in logged content ended the debug output record at that point, so everything the layout rendered after it, including exception text and trailing fields, was silently lost. A party whose data reaches a log message could hide the rest of that record. Only applications on Windows that use OutputDebugStringAppender 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_commit, github_pr.
generic

Pony Mail

https://lists.apache.org/thread.html/gyw2d4ppy82t1vlpdknkfd1nmzp21z17
github_commit

commit 6046fe9d7f35 (apache/logging-log4net)

Fix landed in apache/logging-log4net commit 6046fe9d7f35 — awaiting tagged release

https://github.com/apache/logging-log4net/commit/6046fe9d7f353b49fe995361c071ec2eea8f7ef6
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-2026-105240(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 18× in last 7d / 18× 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 15:53 UTCGHSA enrichment
  3. 2026-10-08 19:36 UTCEG score recompute
  4. 2026-10-08 19:36 UTCGHSA enrichment
  5. 2026-10-08 17:11 UTCEPSS rescore
  6. 2026-10-07 23:47 UTCEPSS rescore
  7. 2026-10-07 17:39 UTCEG score recompute
  8. 2026-10-07 17:39 UTCGHSA enrichment
  9. 2026-10-07 16:44 UTCEG score recompute
  10. 2026-10-07 16:44 UTCGHSA enrichment
  11. 2026-10-07 13:46 UTCGHSA enrichment
  12. 2026-10-07 07:29 UTCEG score recompute
  13. 2026-10-07 07:29 UTCGHSA enrichment
  14. 2026-10-07 06:23 UTCEG score recompute
  15. 2026-10-07 06:23 UTCGHSA enrichment
  16. 2026-10-06 20:32 UTCEG score recompute
  17. 2026-10-06 19:59 UTCEG score recompute
  18. 2026-10-06 19:56 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-105240?
CVE-2026-105240 is a medium vulnerability published on October 6, 2026. Improper Neutralization of Null Byte or NUL Character vulnerability in the OutputDebugStringAppender of Apache log4net. A NUL character in logged content ended the debug output record at that point, so everything the layout rendered after it, including exception text and trailing fields, was…
When was CVE-2026-105240 disclosed?
CVE-2026-105240 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-2026-105240 actively exploited?
CVE-2026-105240 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-2026-105240?
CVE-2026-105240 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-2026-105240?
The CVE record for CVE-2026-105240 names the fix: "Users are recommended to upgrade to version 3.5.0, which fixes the issue." The vendor advisories EchelonGraph has for CVE-2026-105240 are linked in the Vendor Advisories panel on this page.

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