msgpack5: Reserved byte can cause unbounded stream buffering

{
  "id": "e7b8fa711b358e2d991c131f3b197b814d39f2d73400892b55411075b8d53819",
  "url": "https://osv.dev/vulnerability/GHSA-26wq-p25c-j6fv",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "msgpack5: Reserved byte can cause unbounded stream buffering",
    "summary": "### Impact The reserved MessagePack byte `0xc1` is incorrectly treated as incomplete input. When it appears at the start of a decoder stream, all subsequent data is retained while the decoder waits for bytes that can never make the value valid, allowing memory exhaustion. ### Patches The decoder now rejects `0xc1` as invalid input. Streaming decoders release buffered input and stop after unrecoverable decoding errors. ### Workarounds Reject `0xc1` before streaming input to msgpack5, and enforce stream byte and time limits.",
    "evidence": "osv:GHSA-26wq-p25c-j6fv",
    "products": [
      {
        "name": {
          "value": "msgpack5",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.0",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "GHSA-26wq-p25c-j6fv",
      "aliases": [
        "CVE-2026-107299",
        "GHSA-26wq-p25c-j6fv"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "6.1.0"
                }
              ]
            }
          ],
          "package": {
            "name": "msgpack5",
            "purl": "pkg:npm/msgpack5",
            "ecosystem": "npm"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-26wq-p25c-j6fv/GHSA-26wq-p25c-j6fv.json"
          }
        }
      ],
      "modified": "2026-10-08T18:00:08.901031374Z",
      "provider": "osv",
      "references": [
        "https://github.com/mcollina/msgpack5/security/advisories/GHSA-26wq-p25c-j6fv",
        "https://github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d69314",
        "https://github.com/mcollina/msgpack5",
        "https://github.com/mcollina/msgpack5/releases/tag/v6.1.0"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-228"
        ],
        "severity": "MODERATE",
        "github_reviewed": true,
        "nvd_published_at": null,
        "github_reviewed_at": "2026-10-08T17:40:01Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-107299",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 104431,
  "published_at": "2026-10-08T17:40:01+00:00"
}