Security advisory

{
  "id": "99c6187095250706c5ecd067fc7a4cf0fac573d83b9eed3ad83013f198f44a8a",
  "url": "https://osv.dev/vulnerability/CVE-2021-28040",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2021-28040",
    "summary": "An issue was discovered in OSSEC 3.6.0. An uncontrolled recursion vulnerability in os_xml.c occurs when a large number of opening and closing XML tags is used. Because recursion is used in _ReadElem without restriction, an attacker can trigger a segmentation fault once unmapped memory is reached.",
    "evidence": "osv:CVE-2021-28040",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2021-28040",
      "aliases": [
        "CVE-2021-28040"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/ossec/ossec-hids",
              "type": "GIT",
              "events": [
                {
                  "introduced": "9772223c25a3eda512d35026737d7058297039a4"
                },
                {
                  "last_affected": "9772223c25a3eda512d35026737d7058297039a4"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:ossec:ossec:3.6.0:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "3.6.0"
                      },
                      {
                        "last_affected": "3.6.0"
                      }
                    ],
                    "source": "CPE_STRING"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.6.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-28040.json"
          }
        }
      ],
      "modified": "2026-10-20T10:54:35.748424530Z",
      "provider": "osv",
      "references": [
        "https://github.com/ossec/ossec-hids/issues/1953"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2021-28040",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 385690,
  "published_at": "2021-03-05T18:15:13.27+00:00"
}