CVE-2026-1677Medium· 5.3▾ TwilightPoC availableZephyr 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…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 29.2 · likelihood 0 · exploitation 12
A public proof-of-concept already exists for this vulnerability — see Exploit availability below.
Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.
Exploit-prediction probability, daily snapshots since Jul 29.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.2%
Exploit / PoC code exists
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.
zephyr <= 4.3.0Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
Field changes observed since this record was first indexed.
Connected by shared product, vendor, weakness, or advisory.
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