Security advisory

{
  "id": "4716dae15dd8976158e96c535cdc77b1b456ae16197be72533394ecbb0b29fe6",
  "url": "https://osv.dev/vulnerability/CVE-2020-21677",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2020-21677",
    "summary": "A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.",
    "evidence": "osv:CVE-2020-21677",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2020-21677",
      "aliases": [
        "CVE-2020-21677"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/saitoha/libsixel",
              "type": "GIT",
              "events": [
                {
                  "introduced": "686d234ae20f97b9d816d4147ba3f4b90dbae72e"
                },
                {
                  "last_affected": "686d234ae20f97b9d816d4147ba3f4b90dbae72e"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:saitoha:libsixel:1.8.4:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "1.8.4"
                      },
                      {
                        "last_affected": "1.8.4"
                      }
                    ],
                    "source": "CPE_STRING"
                  }
                ]
              }
            }
          ],
          "versions": [
            "1.8.4",
            "v1.8.4"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2020-21677.json"
          }
        }
      ],
      "modified": "2026-10-20T10:52:11.440191054Z",
      "provider": "osv",
      "references": [
        "https://github.com/saitoha/libsixel/issues/123"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2020-21677",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 383443,
  "published_at": "2021-08-10T21:15:07.447+00:00"
}