CVE-2026-1677
net: TLS 1.2 connections allowed on TLS 1.3 sockets
- State
- Published
- Severity
- 5.3 Medium
- Published
- May 11, 2026
- Updated
- Oct 15, 2026
- Reserved
- Jan 30, 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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 5.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N | zephyr |
Weaknesses
- CWE-757 Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')
Affected Products
| Product | Versions |
|---|---|
Zephyrzephyrproject-rtos |
|
References
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