{
  "affected": [
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.13",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.12.1-r1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.14",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.15",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.16",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.17",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.18",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.19",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.20",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.21",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.22",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.23",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "Alpine:v3.24",
        "name": "syncthing",
        "purl": "pkg:apk/alpine/syncthing?arch=source"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.15.1-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "Syncthing is a continuous file synchronization program. In Syncthing before version 1.15.0, the relay server `strelaysrv` can be caused to crash and exit by sending a relay message with a negative length field. Similarly, Syncthing itself can crash for the same reason if given a malformed message from a malicious relay server when attempting to join the relay. Relay joins are essentially random (from a subset of low latency relays) and Syncthing will by default restart when crashing, at which point it's likely to pick another non-malicious relay. This flaw is fixed in version 1.15.0.",
  "id": "ALPINE-CVE-2021-21404",
  "modified": "2026-11-03T06:17:57.988652892Z",
  "published": "2021-04-06T20:15:13.490Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security.alpinelinux.org/vuln/CVE-2021-21404"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2021-21404"
  ]
}