wolfSSLs AVX2-optimized ML-KEM implementation (mlkem_cmp_avx2) compares only 1536 of the 1568 ciphertext bytes during the Fujisaki-Okamoto re-encryption check in ML-KEM-1024 decapsulation. Ciphertexts that differ from the expected re-encryption solely in bytes 1536-1567 bypass implicit rejection and are accepted as valid, breaking IND-CCA2 security. An attacker able to submit chosen ciphertexts to a decapsulation oracle that uses a static ML-KEM-1024 key, and to observe whether the genuine shared secret or the implicit-rejection secret was produced, can use this as a plaintext-checking oracle to recover the private key. A proof of concept recovered a full ML-KEM-1024 private key with approximately 98% success using roughly 350 chosen ciphertexts. The flaw is a deterministic logic error and does not rely on timing measurements.
Weakness
The product compares two entities in a security-relevant context, but the comparison is incorrect.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Wolfssl | Wolfssl | 5.7.0 (including) | 5.9.2 (excluding) |
| Wolfssl | Ubuntu | questing | * |
Extended Description
This Pillar covers several possibilities:
Related Attack Patterns
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