What’s Vulnerable › Vulnerabilities

CVE-2026-106448: StableLib: Prototype poisoning via `__proto__` map keys in CBOR decoding

• Severity: high (CVSS 8.9 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-06 · updated 2026-10-07
• Weakness: CWE-1321

Description

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.

Affected products

• stablelib: before 2.0.4

References

• https://github.com/StableLib/stablelib/commit/0f153a63b7552a0e8721f640984113e419015026
• https://github.com/StableLib/stablelib/releases/tag/@stablelib/cbor@2.0.4
• https://github.com/StableLib/stablelib/security/advisories/GHSA-w48f-fwg7-ww6p

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