{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "02e1e115435888485f2e28b414d267e39e799e07"
            },
            {
              "fixed": "28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed"
            }
          ],
          "repo": "https://gitbox.apache.org/repos/asf/logging-log4net.git",
          "type": "GIT"
        },
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "1.2.9"
              },
              {
                "fixed": "3.5.0"
              }
            ],
            "source": [
              "DESCRIPTION",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "18a96716af733f7c6e4956526acdcc117a1bd461"
            },
            {
              "fixed": "f7794ae187ab2e228e1754cb478568dd305d1b32"
            },
            {
              "fixed": "28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed"
            }
          ],
          "repo": "https://github.com/apache/logging-log4net",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "apache",
    "cwe_ids": [
      "CWE-778"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/105xxx/CVE-2026-105243.json"
  },
  "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": "CVE-2026-105243",
  "modified": "2026-10-09T02:31:06.105693554Z",
  "published": "2026-10-06T19:51:25.116Z",
  "references": [
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/10/07/17"
    },
    {
      "type": "WEB",
      "url": "https://nuget.org/packages"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/105xxx/CVE-2026-105243.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://lists.apache.org/thread.html/jr6fj5skv1vnjbc9jmt8bp151p8ow1rp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-105243"
    },
    {
      "type": "FIX",
      "url": "https://github.com/apache/logging-log4net/commit/28fbfb25678c48a8cc5bc9b94ead0dddfc39ffed"
    },
    {
      "type": "FIX",
      "url": "https://github.com/apache/logging-log4net/pull/315"
    },
    {
      "type": "PACKAGE",
      "url": "https://gitbox.apache.org/repos/asf/logging-log4net.git"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Apache log4net: Oversize EventLogAppender record silently discarded"
}