CVE-2026-1677
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.
Does this matter?
Lower severity and a low EPSS score (0.24%). Track it; it rarely justifies an emergency change on its own.
Description
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.
- CVSS 3.1
- 5.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- EPSS
- 0.24% probability · 16th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-757
- Affected
- zephyrproject/zephyr
- Source
- vulnerabilities@zephyrproject.org
References
- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-23r2-m5wx-4rvqExploit, Patch, Vendor Advisory, Mitigation
- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-23r2-m5wx-4rvqExploit, Patch, Vendor Advisory, Mitigation
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.