{"id":"CVE-2026-1677","title":"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","summary":"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_mi…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","cwe":["CWE-757"],"vendor":"zephyrproject","product":"zephyr","affected":["zephyr <= 4.3.0"],"published":"2026-05-11","updated":"2026-07-08","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-1677","references":[{"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-23r2-m5wx-4rvq","label":"vulnerabilities@zephyrproject.org"},{"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-23r2-m5wx-4rvq","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd"],"epss":0.00243,"epssPercentile":0.15831,"ingestedAt":"2026-07-08T13:51:10.740Z","slug":"CVE-2026-1677","body":"## Overview\n\nZephyr 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.\n\n## Affected\n\n- `zephyr <= 4.3.0`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}