Security advisory

{
  "id": "85df04b28637de36fae39123ce5c9a2c9c8606ec496f3612e7aa65aa55d10083",
  "url": "https://osv.dev/vulnerability/CVE-2021-30027",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2021-30027",
    "summary": "md_analyze_line in md4c.c in md4c 0.4.7 allows attackers to trigger use of uninitialized memory, and cause a denial of service via a malformed Markdown document.",
    "evidence": "osv:CVE-2021-30027",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2021-30027",
      "aliases": [
        "CVE-2021-30027"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/mity/md4c",
              "type": "GIT",
              "events": [
                {
                  "introduced": "aa63198b80f999effed125b55ac16d1cbc9ab21c"
                },
                {
                  "last_affected": "aa63198b80f999effed125b55ac16d1cbc9ab21c"
                },
                {
                  "fixed": "4fc808d8fe8d8904f8525bb4231d854f45e23a19"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:md4c_project:md4c:0.4.7:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0.4.7"
                      },
                      {
                        "last_affected": "0.4.7"
                      }
                    ],
                    "source": "CPE_STRING"
                  },
                  {
                    "range": [
                      {
                        "fixed": "4fc808d8fe8d8904f8525bb4231d854f45e23a19"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "0.4.7",
            "release-0.4.7"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-30027.json",
            "vanir_signatures": [
              {
                "id": "CVE-2021-30027-aafeb3c5",
                "digest": {
                  "length": 10908,
                  "function_hash": "322245608022275724480425469479335526165"
                },
                "source": "https://github.com/mity/md4c/commit/4fc808d8fe8d8904f8525bb4231d854f45e23a19",
                "target": {
                  "file": "src/md4c.c",
                  "function": "md_analyze_line"
                },
                "deprecated": false,
                "signature_type": "Function",
                "signature_version": "v1"
              },
              {
                "id": "CVE-2021-30027-f3156ffc",
                "digest": {
                  "threshold": 0.9,
                  "line_hashes": [
                    "128530702601737101811727024586890550753",
                    "98473776384372157529680730225100509720",
                    "282087636836527325486394792471415280100",
                    "313970169583545866153292837680168776702",
                    "283521056716158467520872169441972465266",
                    "321152261436292213196061633460465514572",
                    "199537899354753774750169400073557411872",
                    "202499592155105600623179137581181437845",
                    "174112236338003714963880316886125584952",
                    "64528996485019690033480507456819749288",
                    "40781584929695501939010212285647372006",
                    "211144263441560594281229750485882864073",
                    "108532761455042207769192576660881309813",
                    "301004014917007072830086453236187746024",
                    "159215856006652495965340164355596265201",
                    "338671760556097010649039124482390622635",
                    "310442026149672368764116397330189875207",
                    "247800360932106444803672585103536412825",
                    "174798969617264694913491682126884538618",
                    "81105429030443539012110219833419686059",
                    "34773241901086520411897294352802850480",
                    "216350882354716231614067117431856901232",
                    "214563497792942822017538392314037574131",
                    "274558718265672796844056938807883132573",
                    "82345420663438109749465528145197249249",
                    "306622871234171740882970515189805638101",
                    "186240891863141040798060690227249672488",
                    "181478689956031745429399673169121431810",
                    "202559148123131947237765628721083981518",
                    "255237651156812476656622229190067102892"
                  ]
                },
                "source": "https://github.com/mity/md4c/commit/4fc808d8fe8d8904f8525bb4231d854f45e23a19",
                "target": {
                  "file": "src/md4c.c"
                },
                "deprecated": false,
                "signature_type": "Line",
                "signature_version": "v1"
              }
            ],
            "vanir_signatures_modified": "2026-10-20T14:24:48Z"
          }
        }
      ],
      "modified": "2026-10-20T14:24:48.506298481Z",
      "provider": "osv",
      "references": [
        "https://github.com/mity/md4c/issues/155",
        "https://github.com/mity/md4c/commit/4fc808d8fe8d8904f8525bb4231d854f45e23a19"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2021-30027",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 388972,
  "published_at": "2021-04-29T15:15:11.02+00:00"
}