# CVE-2026-10665: Heap buffer overflow on WireGuard receive path via unbounded incoming packet length

Status: published. Published: 2026-07-12. Updated: 2026-11-04.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: zephyr) — https://github.com/zephyrproject-rtos/zephyr/commit/6d8bb28dc9064e05e52b5a00b2998ecc663e38cb

## Affected products and versions

- zephyrproject / zephyr (zephyr): ≥ 4.4.0; < 4.4.2 (affected, semver). Source: CNA: zephyr

## Severity and prioritization

- CVSS 3.1: 7.4 (high); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H; source: CNA: zephyr

- CISA KEV: No listing in collected sources

- EPSS: 0.60% as of 2026-11-03; percentile 48.86%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-787

## Exploit evidence

- exploit: https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-3wqm-wgx2-9367 (ADP: CISA-ADP)

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/6d8bb28dc9064e05e52b5a00b2998ecc663e38cb (CNA: zephyr; patch)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-3wqm-wgx2-9367 (CNA: zephyr)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-3wqm-wgx2-9367 (ADP: CISA-ADP; exploit)

## Provenance

- CNA: zephyr: https://www.cve.org/CVERecord?id=CVE-2026-10665; retrieved 2026-11-04; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-10665; retrieved 2026-11-04; source updated Not reported

Revision: e37807b9a8b59dcc768f13f0038d0c3880ee931437666aedf7057fe7b5a98cad

Canonical: https://y2.dev/cve/CVE-2026-10665

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