ruby — security advisory

{
  "id": "cca67bb0e4714f520b8e12839be3149b18169607e953f5740bc414d7c0afc4b6",
  "url": "https://osv.dev/vulnerability/ALPINE-CVE-2026-27820",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ALPINE-CVE-2026-27820",
    "summary": "zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.",
    "evidence": "osv:ALPINE-CVE-2026-27820",
    "products": [
      {
        "name": {
          "value": "ruby",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "3.3.13-r0",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "ruby",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "3.4.9-r0",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "ruby",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "3.4.9-r0",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "ruby",
          "evidence": "/affected/3/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "3.4.9-r0",
            "evidence": "/affected/3/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "ALPINE-CVE-2026-27820",
      "aliases": [
        "ALPINE-CVE-2026-27820"
      ],
      "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": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "3.3.13-r0"
                }
              ]
            }
          ],
          "package": {
            "name": "ruby",
            "purl": "pkg:apk/alpine/ruby?arch=source",
            "ecosystem": "Alpine:v3.21"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-27820.json"
          },
          "ecosystem_specific": {}
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "3.4.9-r0"
                }
              ]
            }
          ],
          "package": {
            "name": "ruby",
            "purl": "pkg:apk/alpine/ruby?arch=source",
            "ecosystem": "Alpine:v3.22"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-27820.json"
          },
          "ecosystem_specific": {}
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "3.4.9-r0"
                }
              ]
            }
          ],
          "package": {
            "name": "ruby",
            "purl": "pkg:apk/alpine/ruby?arch=source",
            "ecosystem": "Alpine:v3.23"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-27820.json"
          },
          "ecosystem_specific": {}
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "3.4.9-r0"
                }
              ]
            }
          ],
          "package": {
            "name": "ruby",
            "purl": "pkg:apk/alpine/ruby?arch=source",
            "ecosystem": "Alpine:v3.24"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-27820.json"
          },
          "ecosystem_specific": {}
        }
      ],
      "modified": "2026-10-27T12:30:04.770953135Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-27820"
      ],
      "references": [
        "https://security.alpinelinux.org/vuln/CVE-2026-27820"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-27820",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 461313,
  "published_at": "2026-04-16T18:16:44.77+00:00"
}