Security advisory

{
  "id": "aef9a9da235bf6a381890bba45c3a239a75d9b0bc1b868ca5fe8b1324e65df57",
  "url": "https://osv.dev/vulnerability/CVE-2021-34813",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2021-34813",
    "summary": "Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.",
    "evidence": "osv:CVE-2021-34813",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2021-34813",
      "aliases": [
        "CVE-2021-34813"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://gitlab.matrix.org/matrix-org/olm",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "d856c441b69fa2d3bb081c35a077725ece3ec0e5"
                },
                {
                  "fixed": "ccc0d122ee1b4d5e5ca4ec1432086be17d5f901b"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:matrix:olm:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.2.3"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "ccc0d122ee1b4d5e5ca4ec1432086be17d5f901b"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.2.2",
            "3.2.1",
            "3.2.0",
            "3.1.5",
            "3.1.4",
            "3.1.3",
            "3.1.2",
            "3.1.1",
            "3.1.0",
            "3.0.0",
            "2.3.0",
            "2.2.2",
            "2.2.1",
            "2.2.0",
            "2.1.0",
            "1.3.0",
            "1.1.0",
            "1.0.0",
            "0.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-34813.json",
            "vanir_signatures": [
              {
                "id": "CVE-2021-34813-240bb04f",
                "digest": {
                  "threshold": 0.9,
                  "line_hashes": [
                    "67187540684594846929930087958775330407",
                    "252238880134199690140829526927907039125",
                    "112731075044979816756838691158599276159",
                    "266670586885842653055159594457029441809",
                    "122863437526258609946485188487153639683",
                    "2322259021207589375720402312402339042",
                    "170628078302948138487804364359809229940",
                    "280008696207157238904539322325357556224",
                    "306982545767147644230375218821142457083",
                    "160271540659833010369177823877678495362",
                    "308281618806135522932869827565222393041",
                    "149136064223153088998885318011358564622",
                    "31400777264479745020044360703052328467",
                    "249163031161303586159027329025144146965",
                    "64992816398013141508940414006691902376",
                    "278982838318123888358918597633323949366",
                    "95614447084228899863388343554603907601",
                    "50985141910277076522136908930418998284",
                    "52922677131880317037314411531219288696",
                    "304011125082188447210728078135368394569",
                    "108512209535030714841988259827627401272",
                    "13058810865725070382559229120526879264",
                    "99818199449007817973156829142645460775"
                  ]
                },
                "source": "https://gitlab.matrix.org/matrix-org/olm@ccc0d122ee1b4d5e5ca4ec1432086be17d5f901b",
                "target": {
                  "file": "src/pk.cpp"
                },
                "deprecated": false,
                "signature_type": "Line",
                "signature_version": "v1"
              },
              {
                "id": "CVE-2021-34813-9e3b972a",
                "digest": {
                  "length": 1070,
                  "function_hash": "147075573380992072531349232456661044906"
                },
                "source": "https://gitlab.matrix.org/matrix-org/olm@ccc0d122ee1b4d5e5ca4ec1432086be17d5f901b",
                "target": {
                  "file": "src/pk.cpp",
                  "function": "olm_pk_decrypt"
                },
                "deprecated": false,
                "signature_type": "Function",
                "signature_version": "v1"
              }
            ],
            "vanir_signatures_modified": "2026-10-20T14:04:47Z"
          }
        }
      ],
      "modified": "2026-10-20T14:04:47.489600529Z",
      "provider": "osv",
      "references": [
        "https://gitlab.matrix.org/matrix-org/olm/-/releases/3.2.3",
        "https://gitlab.matrix.org/matrix-org/olm/-/commit/ccc0d122ee1b4d5e5ca4ec1432086be17d5f901b",
        "https://matrix.org/blog/2021/06/14/adventures-in-fuzzing-libolm"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2021-34813",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 388533,
  "published_at": "2021-06-16T18:15:09.73+00:00"
}