AIKIDO-2026-246457

web-auth/cose-lib is vulnerable to Improper Verification of Cryptographic Signature

Improper Verification of Cryptographic SignatureGHSA-rh56-4rc8-hj58 Published 2 days ago

Medium Risk

This Affects:

web-auth/cose-lib

0.0.1 - 4.7.1

Fixed in 4.7.2

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TL;DR

COSE RSA signature verification does not validate the public exponent of the supplied key before checking a signature. When a key carries a public exponent of 1, the RSA operation s^e mod n reduces to an identity function, so a party that controls the verifying public key produces a signature that verify() accepts for any message across the RS256/RS384/RS512/RS1 and PS256/PS384/PS512 algorithms. This lets forged signatures pass verification without possession of the private key. The fix enforces RFC 8017 public-parameter constraints (an odd exponent with 3 <= e < n) on every RSA sign and verify operation.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range and you verify COSE RSA signatures using key material supplied from an untrusted source.