CVE-2026-106448
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.
| CWE | CWE-1321 |
| Vendor | stablelib |
| Product | stablelib |
| Published | Oct 6, 2026 |
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