CVE-2026-7656
HighCVSS 8.1Exploitation Probability (EPSS)
Low risk24th percentile - higher than 24% of all known CVEs
Summary
A vulnerability in Zephyr RTOS affects IPv6 Neighbor Discovery handlers. Incorrect boolean logic causes all RFC 4861 validity checks (including the mandatory Hop Limit == 255) to be bypassed when the ICMPv6 code field is 0 (normal for ND). This allows an attacker to inject forged RA/NS/NA messages.
Risk Assessment
An adjacent (or remote, due to Hop Limit bypass) attacker can reconfigure the victim's IPv6 settings, poison the neighbor cache, redirect traffic (MITM), or cause denial of service. DNS servers can also be overridden if CONFIG_NET_IPV6_RA_RDNSS is enabled.
Recommendation
Upgrade Zephyr RTOS to a patched version (later than v4.4.0) immediately. If upgrading is not possible, restrict trust in the local network and consider disabling IPv6 ND handling or filtering ICMPv6 traffic at network boundaries.
Other vulnerabilities in Zephyr RTOS
See all- CVE-2026-13480Low
A vulnerability in the LoRaWAN TS004 Fragmented Data Block Transport handler frag_transport_package_callback() in Zephyr RTOS (subsys/lorawan/services/frag_transport.c) lacks validation of remaining payload bytes before each access. An attacker with session keys can cause an out-of-bounds read (up to ~232 bytes) past the RxPayload buffer, copying adjacent static memory into decoder buffers and the FUOTA flash image.
- CVE-2026-13213Medium
A vulnerability in the Hearing Access Service (HAS) in Zephyr RTOS allows a remote (Bluetooth) crash of the HAS peripheral. The issue occurs when a previously bonded client reconnects during the startup window before the application registers the service, leading to an assertion or NULL pointer dereference.
- CVE-2026-12633High
Vulnerability in IPv6 neighbor-discovery code (subsys/net/ip/ipv6_nbr.c) in Zephyr RTOS. The handle_ra_6co() function does not bound the context_len field from the 6CO option in Router Advertisements, leading to a buffer overflow and out-of-bounds memset. An attacker on the same link can send a crafted packet causing a system crash.
- CVE-2026-9771High
A vulnerability in the flash_copy() system call in Zephyr RTOS (with CONFIG_USERSPACE enabled) allows an unprivileged thread to pass forged pointers to flash device structures. Lack of device object validation (src_dev, dst_dev) before dereferencing enables arbitrary code execution in supervisor mode, leading to privilege escalation outside the userspace sandbox.
- CVE-2026-12364High
The vulnerability in Zephyr RTOS concerns the system-call verifier z_vrfy_z_log_msg_static_create(), which did not validate arguments passed to the kernel function. This allows an unprivileged user thread to supply arbitrary pointers and lengths, leading to kernel memory reads and system crashes.
- CVE-2026-12363Medium
The LoRaWAN Fragmented Data Block Transport service (frag_transport.c) does not validate the fragment counter in a received DATA_FRAGMENT command before forwarding it to the decoder. A frag_counter of 0 causes an underflow (frag_counter - 1), leading to an out-of-bounds write (CWE-787) in the default Semtech/LoRaMAC-node decoder, corrupting decoder state and disrupting the firmware-update (FUOTA) session.
- CVE-2026-12233Medium
The PSA Protected Storage credential backend (subsys/net/lib/tls_credentials/tls_credentials_trusted.c) declared its credential-store mutex as a plain zero-filled static struct k_mutex credential_lock; and never called k_mutex_init() on it. A statically zero-filled k_mutex has an uninitialized wait queue (its dlist head/tail are NULL instead of the self-referential sentinels that k_mutex_init/K_MUTEX_DEFINE install). The uncontended lock path does not touch the wait queue, so the defect is latent and serialized use behaves correctly.
- CVE-2026-11812Low
The vulnerability in the UpdateHub subsystem (subsys/mgmt/updatehub/updatehub.c) is due to unsynchronized access to the shared ctx structure. Concurrent operations (background autohandler and user-triggered calls) can write past the fds[1] array, overwriting adjacent struct fields, leading to internal state corruption and denial of service in the firmware update path.
- CVE-2026-10849High
The hawkBit device management client in Zephyr RTOS has a heap-based out-of-bounds write vulnerability. The response buffer lacks space for a terminating null byte, causing a single null byte write past the allocated memory when the response length matches the buffer size.
- CVE-2026-10848High
In the OCPP 1.6 client in Zephyr RTOS, a vulnerability was found involving out-of-bounds buffer read during WAMP RPC frame parsing. The extract_string_field() function uses strncpy without guaranteed null-termination, leading to reads beyond the 128-byte buffer and potential out-of-bounds null write. The vulnerability can be remotely exploited by a malicious central server or an on-path attacker.
Original NVD description (English source)
The IPv6 Neighbor Discovery handlers in subsys/net/ip/ipv6_nbr.c (handle_ra_input, handle_ns_input, handle_na_input) used an incorrect boolean expression that combined the RFC 4861 validity checks with the ICMPv6 code check using the wrong operator precedence: the form was ((length/hop/source/target checks) && (icmp_hdr->code != 0)). Because every legitimate ND message carries ICMPv6 code 0, an attacker setting code == 0 (the normal value) caused the entire predicate to evaluate false, so the packet was never dropped and all of the other checks were silently skipped. The bypassed checks include the mandatory Hop Limit == 255 verification (which proves an ND packet originated on-link and was not forwarded) and, for Router Advertisements, the requirement that the source be a link-local address, as well as multicast-target sanity checks. As a result, an adjacent on-link attacker — and, because the Hop-Limit-255 guard is bypassed, potentially a remote/off-link attacker whose packets would otherwise be rejected — can have forged Router Advertisement, Neighbor Solicitation, and Neighbor Advertisement messages accepted. A forged RA lets the attacker reconfigure the victim's default router, on-link prefixes (SLAAC), MTU, reachable/retransmit timers, and (with CONFIG_NET_IPV6_RA_RDNSS) DNS servers, while forged NS/NA enable neighbor-cache poisoning, enabling man-in-the-middle, traffic redirection, and denial of service. The flaw is an input-validation/authentication weakness rather than a memory-safety issue: the underlying packet-parsing primitives (net_pkt_get_data, net_pkt_read, net_pkt_skip) are independently bounds-safe and the validated length is the true buffer length, so skipping the length check causes no out-of-bounds access. The defect has existed since the logic was introduced in 2018 and shipped in all releases through v4.4.0; it is fixed by splitting the condition so any failing check drops the packet.