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.
Published: 2026-05-11
Score: 5.3 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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History

Mon, 11 May 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 11 May 2026 07:45:00 +0000

Type Values Removed Values Added
First Time appeared Zephyrproject-rtos
Zephyrproject-rtos zephyr
Vendors & Products Zephyrproject-rtos
Zephyrproject-rtos zephyr

Mon, 11 May 2026 06:15:00 +0000

Type Values Removed Values Added
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.
Title net: TLS 1.2 connections allowed on TLS 1.3 sockets
Weaknesses CWE-757
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}


Subscriptions

Zephyrproject-rtos Zephyr
cve-icon MITRE

Status: PUBLISHED

Assigner: zephyr

Published:

Updated: 2026-05-11T16:31:22.202Z

Reserved: 2026-01-30T05:38:22.811Z

Link: CVE-2026-1677

cve-icon Vulnrichment

Updated: 2026-05-11T16:30:42.454Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-05-11T06:16:08.683

Modified: 2026-05-13T15:25:04.383

Link: CVE-2026-1677

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-11T08:00:12Z

Weaknesses