{"id":"CVE-2026-8718","title":"Out-of-bounds write in DTLS peer Connection ID getsockopt (`TLS_DTLS_PEER_CID_VALUE`) in Zephyr net sockets/TLS","summary":"tls_opt_dtls_peer_connection_id_value_get() in subsys/net/lib/sockets/sockets_tls.c, which handles getsockopt(SOL_TLS, TLS_DTLS_PEER_CID_VALUE), passed the caller-supplied optval directly to mbedtls_ssl_get_peer_cid() without verifying t…","severity":"high","cvss":8.4,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H","cvssSource":"cna","cwe":["CWE-787"],"vendor":"zephyrproject","product":"zephyr","affected":["zephyr >= 3.5.0 < 4.3.2","zephyr >= 4.4.0 < 4.4.1"],"ssvc":{"exploitation":"poc","automatable":"no","technicalImpact":"partial","timestamp":"2026-08-12T18:49:17.354008Z"},"exploitAvailable":true,"published":"2026-08-10","updated":"2026-11-04","sourceUpdated":"2026-11-04T04:59:18.089Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-8718","references":[{"url":"https://github.com/zephyrproject-rtos/zephyr/commit/aa317825a55a401315e8e17f620c70c02e8f176d","label":"Fix commit"},{"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-p3r6-mx6c-33gq","label":"GHSA-p3r6-mx6c-33gq"}],"tags":["cve.org","exploit-available"],"epss":0.00171,"epssPercentile":0.06491,"ingestedAt":"2026-11-05T20:33:06.699Z","slug":"CVE-2026-8718","body":"## Overview\n\ntls_opt_dtls_peer_connection_id_value_get() in subsys/net/lib/sockets/sockets_tls.c, which handles getsockopt(SOL_TLS, TLS_DTLS_PEER_CID_VALUE), passed the caller-supplied optval directly to mbedtls_ssl_get_peer_cid() without verifying the buffer was at least MBEDTLS_SSL_CID_OUT_LEN_MAX (default 32) bytes. mbedtls_ssl_get_peer_cid() copies the peer-negotiated DTLS Connection ID (length 1..MBEDTLS_SSL_CID_OUT_LEN_MAX) into that buffer without a destination-size parameter, so a caller-supplied optlen smaller than the CID causes a write of up to 31 bytes past the buffer end.\n\nIn CONFIG_USERSPACE builds the getsockopt syscall verifier (z_vrfy_zsock_getsockopt) bounce-buffers the user's optval into a kernel allocation of exactly optlen bytes (k_usermode_alloc_from_copy -> z_thread_malloc), so an unprivileged user thread that passes a small optlen on a connected DTLS socket with Connection ID enabled induces a kernel-heap buffer overflow, with the overflowing content being the remote peer's CID.\n\nThe defect requires CONFIG_MBEDTLS_SSL_DTLS_CONNECTION_ID, an established DTLS session with a negotiated peer CID, and (for the kernel-crossing case) CONFIG_USERSPACE. Introduced when the TLS_DTLS_CID option was added (v3.5.0).\n\nThe fix rejects callers whose optlen is below MBEDTLS_SSL_CID_OUT_LEN_MAX with -EINVAL.\n\n## Affected\n\n- `zephyr >= 3.5.0 < 4.3.2`\n- `zephyr >= 4.4.0 < 4.4.1`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":58,"depthScoreParts":{"impact":46.2,"likelihood":0,"exploitation":12,"ransomware":0},"changes":[]}