The flaw resides in wc_PKCS7_DecodeAuthEnvelopedData, which omits a lower bound check on the AES‑GCM authentication tag length. An attacker can truncate the MAC field from the proper 16 bytes to 1 byte, reducing the tag verification probability from 2⁻¹²⁸ to 2⁻⁸ and allowing the encrypted data to be processed without authenticating it. This constitutes a bypass of the integrity check and enables unauthorized disclosure of encrypted secrets.

wolfSSL software that implements the PKCS#7 envelope decoding routine is affected. The specific version is not listed, so any release that includes the vulnerable wc_PKCS7_DecodeAuthEnvelopedData implementation may be impacted.

The CVSS score of 8.7 indicates high severity. Although exact EPSS data is unavailable, the vulnerability involves a known denial of verification and is not listed in CISA's KEV catalogue, suggesting it is not yet widely exploited. The likely attack vector is a man‑in‑the‑middle positioned on the channel carrying PKCS#7 enveloped data, capable of truncating the MAC field. Because the bug removes a critical integrity check, successful exploitation would give an attacker unauthorized access to the decrypted payload.