https://w1.fi/cgit/hostap-www/commit/?id=a28b295e9920bee4cb58b90df9671c8cb3e07da5
When using WPA2, EAPOL-Key frames that had the Encrypted flag set but not the MIC flag, had their data field decrypted without first verifying the MIC. In case the data field was encrypted using RC4 (i.e., when negotiating TKIP as the pairwise cipher), this meant thatunauthenticated but decrypted data would then be processed. An adversary could abuse this as a decryption oracle to recover sensitive information in the data field of EAPOL-Key messages (e.g., the group key).