Heap buffer overflow on WireGuard receive path via unbounded incoming packet length

Summary

In Zephyr's WireGuard subsystem (subsys/net/lib/wireguard), wg_process_data_message() in wg_crypto.c linearizes an inbound transport-data payload into a fixed pool buffer of CONFIG_WIREGUARD_BUF_LEN bytes before decryption. The call net_buf_linearize(buf->data, data_len, pkt->buffer, ..., data_len) passed the attacker-derived data_len as both the destination capacity and the copy length, defeating the function's internal len = min(len, dst_len) bound. data_len is derived from the received UDP datagram length and is only lower-bounded by wg_ctrl_recv() (no upper bound). When data_len exceeds CONFIG_WIREGUARD_BUF_LEN — e.g. when the buffer length is lowered below the link MTU, on links with MTU above the buffer size, or via reassembled IPv4/IPv6 fragments that exceed it — the underlying memcpy writes past the end of the pool buffer, an out-of-bounds write (CWE-787). The overflow occurs before the Poly1305 authentication check, so it requires only a valid receiver session index rather than a valid authenticator, and is reachable by a malicious or compromised peer (or an on-path attacker driving an established session) over the network, yielding remote memory corruption and at minimum a reliable denial of service. The defect was present in the WireGuard implementation shipped in Zephyr 4.4.0. The fix adds an explicit data_len > CONFIG_WIREGUARD_BUF_LEN rejection and corrects the linearize call to pass net_buf_max_len(buf) as the destination capacity.

Timeline

1. Jul 12, 2026, 4:16 PM UTCCVE published
2. Jul 13, 2026, 3:48 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: no · Technical impact: partial

3. Oct 15, 2026, 10:10 PM UTCRecord last updated

Affected versions

• zephyr

  From 4.4.0 · fixed in 4.4.2

References 2