log4net — security advisory

{
  "id": "b197cbfed9fb35a9da16bec498b23dfdff16601b49b9df18e5a42e8601a245d4",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-105243",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2026-105243",
    "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.",
    "evidence": "osv:DEBIAN-CVE-2026-105243",
    "products": [
      {
        "name": {
          "value": "log4net",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.2.10+dfsg-10",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "1.2.10+dfsg-9",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "log4net",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.2.10+dfsg-10",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "1.2.10+dfsg-9",
            "evidence": "/affected/1/versions"
          }
        ]
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "DEBIAN-CVE-2026-105243",
      "aliases": [
        "DEBIAN-CVE-2026-105243"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "log4net",
            "purl": "pkg:deb/debian/log4net?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "versions": [
            "1.2.10+dfsg-10",
            "1.2.10+dfsg-9"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-105243.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "log4net",
            "purl": "pkg:deb/debian/log4net?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "versions": [
            "1.2.10+dfsg-10",
            "1.2.10+dfsg-9"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-105243.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-10T09:47:47.308254516Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-105243"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2026-105243"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-105243",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 228537,
  "published_at": "2026-10-06T20:17:16.167+00:00"
}