# CVE-2026-1677

## Summary

- **CVE ID:** CVE-2026-1677
- **Severity:** MEDIUM
- **CVSS Score:** 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)
- **CWE:** CWE-757
- **Published:** May 11, 2026
- **Last Modified:** May 11, 2026

## 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.

## Affected Products

- zephyrproject-rtos — Zephyr (*)

## References

- [CNA](https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-23r2-m5wx-4rvq)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.24%
- **EPSS Percentile:** 15.5

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._