Zephyr sockets created with IPPROTO_TLS_1_3 can still negotiate a TLS 1.2 connection when both TLS versions are enabled in Kconfig, because the socket-level protocol selection is not propagated to mbedTLS (e.g. via mbedtls_ssl_conf_min_tls_version). The ClientHello advertises both versions and the peer can establish TLS 1.2, so applications that assumed IPPROTO_TLS_1_3 enforces TLS 1.3 may silently use TLS 1.2 and remain exposed to TLS 1.2-specific weaknesses. As a workaround, the TLS_CIPHERSUITE_LIST socket option can be restricted to TLS 1.3-only cipher suites.
{
"cna_assigner": "zephyr",
"cwe_ids": [
"CWE-757"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/1xxx/CVE-2026-1677.json"
}