The bug is in wolfSSL's implementation of encrypt-then-MAC. When the build flag HAVE_ENCRYPT_THEN_MAC is defined, the library is supposed to enforce encrypt-then-MAC but instead can revert to MAC-then-Encrypt. This flaw undermines the authenticated‑encryption guarantee, potentially allowing an attacker to remove or alter the authentication tag without detection. The weakness is classified as CWE‑757, which covers improper cryptographic fallback.

Affected systems are any installations of the wolfSSL library when built with HAVE_ENCRYPT_THEN_MAC enabled. Version information is not specified, so any build that includes the buggy code path could be vulnerable. Organizations should verify whether their wolfSSL version is compiled with that option and consult vendor releases for a patch.

The CVSS score of 2.1 indicates a low severity assessment, and EPSS data is not available. The vulnerability is not listed in CISA KEV. Exploitation would require an attacker to influence the cryptographic configuration or the mode selection, which is unlikely to be achieved automatically in a remote network attack. Therefore, the risk is modest, but addressing the issue is prudent to maintain proper cryptographic integrity.