ZephyrProject Zephyr up to 4.4.2 Ethernet L2 ethernet.c ethernet_fill_header memory corruption

Summaryinfo

A vulnerability categorized as critical has been discovered in ZephyrProject Zephyr up to 4.4.2. The impacted element is the function ethernet_fill_header of the file subsys/net/l2/ethernet/ethernet.c of the component Ethernet L2. Such manipulation leads to memory corruption. This vulnerability is uniquely identified as CVE-2026-82962. The attack can be launched remotely. No exploit exists. Applying a patch is advised to resolve this issue.

Detailsinfo

A vulnerability was found in ZephyrProject Zephyr up to 4.4.2 and classified as critical. Affected by this issue is the function ethernet_fill_header of the file subsys/net/l2/ethernet/ethernet.c of the component Ethernet L2. The manipulation with an unknown input leads to a memory corruption vulnerability. Using CWE to declare the problem leads to CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. Impacted is integrity, and availability. CVE summarizes:

ethernet_fill_header() in subsys/net/l2/ethernet/ethernet.c can prepend the Ethernet header in place, by pushing it into the headroom of the packet's first fragment, instead of allocating a separate header fragment. Before this fix the in-place path was selected purely from the build-time value of CONFIG_NET_L2_ETHERNET_RESERVE_HEADER, with no check that the packet actually has that headroom, and then called net_buf_push(pkt->buffer, hdr_len). Only Ethernet TX allocations reserve that space: net_pkt_alloc_buffer() invokes the L2 alloc hook (ethernet_l2_alloc()) only when is_pkt_tx() is true and the packet's interface is the Ethernet interface. A packet that was allocated by a different L2 and then handed to Ethernet for transmission therefore has too little (usually zero) headroom. Such packets are produced by ordinary routing and tunnelling paths: net_route_packet_if() re-targets a received packet to another interface when CONFIG_NET_IPV4_FORWARDING / CONFIG_NET_IPV6_FORWARDING are enabled (for example an 802.15.4/OpenThread or PPP interface forwarding to Wi-Fi/Ethernet), net_route_ipv6_mcast_forward_packet() forwards an RX-slab clone that carries no reserve, and the IPIP tunnel interface_send() prepends an outer IP header allocated on the virtual interface. In these configurations a remote or adjacent attacker triggers the condition simply by sending traffic that the device forwards. Because net_buf_simple_push() only asserts on the headroom bound, a build without CONFIG_ASSERT (and without the newer CONFIG_NET_BUF_HARDENING) moves the fragment data pointer below the start of its data block and writes 14 bytes — 18 with VLAN — of Ethernet header out of bounds. With the default fixed-size buffer pools this overwrites the tail of the neighbouring buffer's payload or memory preceding the pool array; with variable-size pools it overwrites the buffer reference count and the heap chunk header. The attacker controls neither the written bytes nor the offset, so the practical impact is memory corruption leading to a crash, packet corruption, or heap inconsistency rather than controlled code execution. The fix takes the in-place path only when net_buf_headroom(pkt->buffer) is large enough and otherwise falls back to a separate header fragment.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-82962 since 08/31/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available.

Applying the patch b39f86ea61d0a0fdd7e9f145110649394e2c22ca is able to eliminate this problem.

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Productinfo

Type

• Project Management Software

Vendor

• ZephyrProject

Name

• Zephyr

Version

• 4.4.0
• 4.4.1
• 4.4.2

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CPE 2.2info

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