Vulnerability in Zephyrproject Zephyr
CVE-2026-1677
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 · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.002 (14.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 14th percentile — 14.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
Weakness classification (CWE)
References
- github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-23r2-m5wx-4rvq (Exploit, Patch, Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-1677?
- CVE-2026-1677 is a medium-severity vulnerability in Zephyrproject Zephyr, classified under CWE-757. CVSS score: 5.3/10. Published 2026-05-11.
- How severe is CVE-2026-1677?
- Medium severity. CVSS v3 base score is 5.3 out of 10.