Zephyr Project up to 4.4.1 ICMPv6 Error subsys/net/ip/icmpv6.c net_icmpv6_send_error allocation of resources

Summaryinfo

A vulnerability, which was classified as critical, was found in Zephyr Project Zephyr up to 4.4.1. Affected by this vulnerability is the function net_icmpv6_send_error of the file subsys/net/ip/icmpv6.c of the component ICMPv6 Error Handler. Such manipulation leads to allocation of resources. This vulnerability is listed as CVE-2026-16515. The attack may be performed from remote. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Zephyr Project Zephyr up to 4.4.1. It has been rated as critical. Affected by this issue is the function net_icmpv6_send_error of the file subsys/net/ip/icmpv6.c of the component ICMPv6 Error Handler. The manipulation with an unknown input leads to a allocation of resources vulnerability. Using CWE to declare the problem leads to CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. Impacted is availability. CVE summarizes:

net_icmpv6_send_error() in subsys/net/ip/icmpv6.c implemented only one of the three RFC 4443 section 2.4 suppression rules (do not answer an ICMPv6 error with an ICMPv6 error). It did not check whether the triggering packet's source address identifies a single node (rule e.6) or whether the packet was sent to a multicast destination (rule e.3, whose only exceptions are Packet Too Big and Parameter Problem Code 2). Of the five call sites, only the port-unreachable path in subsys/net/ip/connection.c carried an equivalent guard of its own; the extension-header, unknown-next-header and fragmentation paths in subsys/net/ip/ipv6.c and subsys/net/ip/ipv6_fragment.c had none. An unauthenticated attacker with access to the same link can exploit this in two ways. Sending a single IPv6 packet to the link-local all-nodes group ff02::1 carrying an unrecognized next-header value, with the source address spoofed to a chosen victim, causes every Zephyr node on the link to emit an ICMPv6 Parameter Problem message to that victim — a reflector with an amplification factor equal to the number of nodes. Alternatively, sending a unicast packet whose source address is a multicast address causes the node to transmit its ICMPv6 error to that multicast address, turning one unicast packet into a link-flooded multicast frame. Packets addressed to ff02::1 are accepted unconditionally by ipv6_input(), and no check rejects a multicast source address, so no special configuration is required. The impact is degraded availability of the shared link and of the reflection victim, together with the ability for the attacker to hide its own address behind the responding nodes. The effect is amplified on constrained mesh links such as 802.15.4/Thread, where link-local multicast is flooded hop by hop. There is no memory-safety consequence: the error packet itself is well formed, it is simply emitted in cases where the protocol forbids it. The fix adds both suppression checks at the single choke point in net_icmpv6_send_error(), before any reply packet is allocated, preserving the RFC-mandated exceptions for NET_ICMPV6_PACKET_TOO_BIG and Parameter Problem Code 2. Note that the IPv4 counterpart net_icmpv4_send_error() in subsys/net/ip/icmpv4.c still checks only for a broadcast destination and retains an equivalent gap for multicast destinations and non-unique sources.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-16515 since 07/21/2026. 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. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 4.4.2 eliminates this vulnerability. Applying the patch ba4247b24ddd3a5360b617e3ca17131ca9e8026a is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Project Management Software

Vendor

• Zephyr Project

Name

• Zephyr

Version

• 4.4.0
• 4.4.1

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CPE 2.2info

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