StableLib: Prototype poisoning via `__proto__` map keys in CBOR decoding
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 sourcePublished 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": [
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"repo": "https://github.com/stablelib/stablelib",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "fc5ed95550b1deba7fa2f1418a174fa003546465"
},
{
"fixed": "0f153a63b7552a0e8721f640984113e419015026"
}
],
"database_specific": {
"extracted_events": [
{
"range": [
{
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},
{
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],
"source": "AFFECTED_FIELD",
"strategy": "StringRangeExpression"
},
{
"range": [
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}
],
"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"
}