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StableLib: Prototype poisoning via `__proto__` map keys in CBOR decoding

Type: advisorySources: OSV

StableLib is a stable library of useful TypeScript and JavaScript code. Prior to 2.0.4, the @stablelib/cbor CBOR map decoding path creates ordinary JavaScript objects and assigns attacker-controlled keys with bracket assignment. A map key named __proto__ invokes the inherited prototype setter instead of creating an ordinary own property, allowing the decoded object's prototype to contain attacker-controlled authorization or feature-flag values. Downstream code that trusts normal property lookup or merges the decoded object can therefore make security-sensitive decisions using inherited attacker data. This issue is fixed in version 2.0.4.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-106448
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 16:34 UTC · Revision 1

Source evidence

StableLib: Prototype poisoning via `__proto__` map keys in CBOR decoding

core-osv · Original source

Published 6 Oct 2026, 19:45 UTC

StableLib is a stable library of useful TypeScript and JavaScript code. Prior to 2.0.4, the @stablelib/cbor CBOR map decoding path creates ordinary JavaScript objects and assigns attacker-controlled keys with bracket assignment. A map key named __proto__ invokes the inherited prototype setter instead of creating an ordinary own property, allowing the decoded object's prototype to contain attacker-controlled authorization or feature-flag values. Downstream code that trusts normal property lookup or merges the decoded object can therefore make security-sensitive decisions using inherited attacker data. This issue is fixed in version 2.0.4.

osv:CVE-2026-106448
Complete source record
{
  "id": "ddfbfbe2f58bea4970ef84a1a7b9fa5ea27362187eb68996f4f2345e2e6f155c",
  "url": "https://osv.dev/vulnerability/CVE-2026-106448",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "StableLib: Prototype poisoning via `__proto__` map keys in CBOR decoding",
    "summary": "StableLib is a stable library of useful TypeScript and JavaScript code. Prior to 2.0.4, the @stablelib/cbor CBOR map decoding path creates ordinary JavaScript objects and assigns attacker-controlled keys with bracket assignment. A map key named __proto__ invokes the inherited prototype setter instead of creating an ordinary own property, allowing the decoded object's prototype to contain attacker-controlled authorization or feature-flag values. Downstream code that trusts normal property lookup or merges the decoded object can therefore make security-sensitive decisions using inherited attacker data. This issue is fixed in version 2.0.4.",
    "evidence": "osv:CVE-2026-106448",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-106448",
      "aliases": [
        "CVE-2026-106448",
        "GHSA-w48f-fwg7-ww6p"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/stablelib/stablelib",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "fc5ed95550b1deba7fa2f1418a174fa003546465"
                },
                {
                  "fixed": "0f153a63b7552a0e8721f640984113e419015026"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "2.0.4"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "0f153a63b7552a0e8721f640984113e419015026"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
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          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-106448.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.281298979Z",
      "provider": "osv",
      "references": [
        "https://github.com/StableLib/stablelib/releases/tag/@stablelib/cbor@2.0.4",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/106xxx/CVE-2026-106448.json",
        "https://github.com/StableLib/stablelib/security/advisories/GHSA-w48f-fwg7-ww6p",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-106448",
        "https://github.com/StableLib/stablelib/commit/0f153a63b7552a0e8721f640984113e419015026"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1321"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/106xxx/CVE-2026-106448.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-106448",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504750,
  "published_at": "2026-10-06T19:45:02.616+00:00"
}