MapServer has heap buffer overflow in SLD `Categorize` Threshold parsing

{
  "id": "5be7a3ffd8d4cb3e93771f0ab98e6f126d4307238e49c75d488a717bd34d21a8",
  "url": "https://osv.dev/vulnerability/CVE-2026-33721",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "MapServer has heap buffer overflow in SLD `Categorize` Threshold parsing",
    "summary": "MapServer is a system for developing web-based GIS applications. Starting in version 4.2 and prior to version 8.6.1, a heap-buffer-overflow write in MapServer’s SLD (Styled Layer Descriptor) parser lets a remote, unauthenticated attacker crash the MapServer process by sending a crafted SLD with more than 100 Threshold elements inside a ColorMap/Categorize structure (commonly reachable via WMS GetMap with SLD_BODY). Version 8.6.1 patches the issue.",
    "evidence": "osv:CVE-2026-33721",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-33721",
      "aliases": [
        "CVE-2026-33721",
        "GHSA-cv4m-mr84-fgjp"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/mapserver/mapserver",
              "type": "GIT",
              "events": [
                {
                  "introduced": "8d58e49d129e88e3d319f02be3c8ca65ae7d6de8"
                },
                {
                  "fixed": "292d06f99f427ff4ea54720849659cbd9f8cfef8"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "4.2"
                      },
                      {
                        "fixed": "8.6.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "292d06f99f427ff4ea54720849659cbd9f8cfef8"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "rel-8-6-1"
                  },
                  {
                    "cpe": "cpe:2.3:a:osgeo:mapserver:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "4.2.0"
                      },
                      {
                        "fixed": "8.6.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33721.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:26.655735300Z",
      "provider": "osv",
      "references": [
        "https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1",
        "https://lists.debian.org/debian-lts-announce/2026/04/msg00017.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33721.json",
        "https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-33721"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-787"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33721.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-33721",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 493361,
  "published_at": "2026-03-27T00:15:00.36+00:00"
}