CVE-2026-8718 Out-of-bounds write in DTLS peer Connection ID getsockopt (`TLS_DTLS_PEER_CID_VALUE`) in Zephyr net sockets/TLS
An out-of-bounds write in Zephyr's DTLS getsockopt handler allows kernel heap corruption, potentially leading to privilege escalation or code execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-8718?
CVE-2026-8718 is a high-severity memory corruption vulnerability in zephyrproject zephyr, published on 10 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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 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.
In 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.
The 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).
The fix rejects callers whose optlen is below MBEDTLS_SSL_CID_OUT_LEN_MAX with -EINVAL.
Weakness: CWE-787
Which versions are affected by CVE-2026-8718?
How do I fix CVE-2026-8718?
No fix has been published for CVE-2026-8718 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-8718 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-8718 exists.
Sources
Also known as GHSA-p3r6-mx6c-33gq.