AIKIDO-2026-763881
webauthn is vulnerable to Improper Input Validation
43
Medium Risk
This Affects:
webauthnTL;DR
The parse_cbor helper decodes CBOR from WebAuthn attestation and authenticator responses without rejecting duplicate map keys. Because Python treats True and integer 1 as the same dictionary key, a crafted response can silently overwrite COSE key parameters such as kty, causing an EC2 key structure to be interpreted as an RSA key. The same duplicate-key collision can downgrade the attestation format (for example packed to none) or swap the declared curve, undermining verification of the response. The fix decodes CBOR with allow_duplicate_keys=False so responses containing duplicate map keys are rejected as invalid.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range.
Background info
webauthn is vulnerable to Improper Input Validation in versions 1.0.0 - 2.8.0.
How to fix this
Upgrade the webauthn library to the patch version.
Are You Affected?
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