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GHSA-J8MM-W573-8V6C

Vulnerability from github – Published: 2026-10-06 21:31 – Updated: 2026-10-06 21:31

Details

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.

Severity

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

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{
  "affected": [],
  "aliases": [
    "CVE-2026-105243"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-778"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-06T20:17:16Z",
    "severity": "MODERATE"
  },
  "details": "Insufficient Logging vulnerability in the EventLogAppender of Apache log4net.\n\nLong 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.\n\nThis issue affects Apache log4net: from 1.2.9 before 3.5.0.\n\nUsers are recommended to upgrade to version 3.5.0, which fixes the issue.",
  "id": "GHSA-j8mm-w573-8v6c",
  "modified": "2026-10-06T21:31:59Z",
  "published": "2026-10-06T21:31:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-105243"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apache/logging-log4net/pull/315"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed"
    },
    {
      "type": "WEB",
      "url": "https://lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rp"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-105243 (GCVE-0-2026-105243)

Vulnerability from cvelistv5 – Published: 2026-10-06 19:51 – Updated: 2026-10-06 19:51

Title

Apache log4net: Oversize EventLogAppender record silently discarded

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.

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CWE

CWE-778 - Insufficient Logging

Assigner

apache mitre root Scorecard

References

3 references

URL	Tags
https://github.com/apache/logging-log4net/pull/315	patch
https://github.com/apache/logging-log4net/commit/…	patch
https://lists.apache.org/thread.html/jr6fj5skv1vn…	vendor-advisory

Impacted products

2 products

Vendor	Product	Version
Apache Software Foundation	Apache log4net	Affected: 1.2.9 , < 3.5.0 (semver)
Apache Software Foundation	Apache log4net	Affected: 02e1e115435888485f2e28b414d267e39e799e07 , < 28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed (git)

Credits

The Apache Software Foundation Claude Security Jan Friedrich

Show details on NVD website

JSON

To clipboard

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      "affected": [
        {
          "collectionURL": "https://nuget.org/packages",
          "defaultStatus": "unaffected",
          "packageName": "log4net",
          "packageURL": "pkg:nuget/log4net",
          "product": "Apache log4net",
          "vendor": "Apache Software Foundation",
          "versions": [
            {
              "lessThan": "3.5.0",
              "status": "affected",
              "version": "1.2.9",
              "versionType": "semver"
            }
          ]
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          "value": "Claude Security"
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          "lang": "en",
          "type": "remediation developer",
          "value": "Jan Friedrich"
        }
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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GHSA-J8MM-W573-8V6C

CVE-2026-105243 (GCVE-0-2026-105243)

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