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CVE-2026-13735— WireGuard keepalive transport-data messages accepted without Poly1305 authentication

Quick assessment

Affected
zephyrproject zephyr
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Zephyr 中 WireGuard 的实现（位于 ）对 keepalive（保活）数据包的处理存在缺陷。在 函数中，任何载荷长度恰好为 16 字节的类型 4 传输数据消息（即由空明文加上一个纯 Poly1305 认证标签组成的保活包）会被直接接受并立即返回，而从未调用 进行解密。因此，Poly1305 认证标签从未被验证；在此之前，仅有的检查包括：基于攻击者提供的 进行的明文接收方索引查找（ ），以及非加密的密钥对有效性/过期检查。 该路径完全可以通过网络访问：进入 WireGuard 端口的入站 UDP 数据包

CVSS 3.7 · Low
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I. Basic Information for CVE-2026-13735

Vulnerability Information
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Vulnerability Title
WireGuard keepalive transport-data messages accepted without Poly1305 authentication
Source: CVE Program / CVE List V5
Vulnerability Description
Zephyr's WireGuard implementation in subsys/net/lib/wireguard/wg_crypto.c mishandled keepalive packets. In wg_process_data_message(), any type-4 transport-data message whose payload was exactly 16 bytes (an empty plaintext plus a bare Poly1305 tag, i.e. a keepalive) was accepted and returned immediately, before wg_decrypt_packet() was ever called. The Poly1305 authentication tag was therefore never verified; the only preceding gates were a cleartext receiver-index lookup (get_peer_keypair_for_index() on the attacker-supplied data_hdr->receiver) and a non-cryptographic keypair validity/expiry check. The path is reachable entirely from the network: inbound UDP on the WireGuard port is dispatched by wg_input() to handle_transport_data() and then wg_process_data_message(). The 32-bit receiver index is transmitted in cleartext in WireGuard handshake and data messages, so an on-path observer learns it directly and an off-path attacker can brute-force it against the UDP port. Given an active receiving-valid session for that index, an attacker could send a 16-byte garbage payload and have it accepted without possessing the session key. On acceptance the unauthenticated message caused the management layer to observe a spoofed NET_EVENT_VPN_CONNECTED signal (setting peer->first_valid and notifying any net_mgmt listener) and incremented the keepalive-RX statistic. The impact is limited to integrity of this status signal: no plaintext is decrypted or injected, no key is disclosed, and the early-return path did not update the peer endpoint or liveness timers, so there is no traffic-injection, session-takeover, or availability consequence. The fix removes the pre-decrypt early return so a 16-byte payload flows through wg_decrypt_packet(), which verifies the Poly1305 tag over the empty plaintext, followed by the existing anti-replay check; only an authenticated, non-replayed message is then recognised as a keepalive. Forged keepalives now fail the tag check and are counted as decrypt failures.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
使用欺骗进行的认证绕过
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
zephyrproject zephyr 4.4.0 ~ 4.4.2 -

II. Public POCs for CVE-2026-13735

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III. Intelligence Information for CVE-2026-13735

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Patches & Fixes for CVE-2026-13735 (1)

Vendor Advisories for CVE-2026-13735 (1)

IV. Related Vulnerabilities

Same product: zephyr
Same vendor: zephyrproject
Same weakness: CWE-290

V. Comments for CVE-2026-13735

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