ZephyrProject Zephyr up to 4.4.1 Neighbor Discovery subsys/net/ip/net_if.c net_if_ipv6_calc_reachable_time base_reachable_time denial of service

Summaryinfo

A vulnerability was found in ZephyrProject Zephyr up to 4.4.1. It has been classified as critical. This vulnerability affects the function net_if_ipv6_calc_reachable_time of the file subsys/net/ip/net_if.c of the component Neighbor Discovery. This manipulation of the argument base_reachable_time causes denial of service. This vulnerability is handled as CVE-2026-15893. The attack can be initiated remotely. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in ZephyrProject Zephyr up to 4.4.1 and classified as critical. Affected by this vulnerability is the function net_if_ipv6_calc_reachable_time of the file subsys/net/ip/net_if.c of the component Neighbor Discovery. The manipulation of the argument base_reachable_time with an unknown input leads to a denial of service vulnerability. The CWE definition for the vulnerability is CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. As an impact it is known to affect availability. The summary by CVE is:

net_if_ipv6_calc_reachable_time() in subsys/net/ip/net_if.c derives a randomized ND reachable time from ipv6->base_reachable_time as min_reachable + sys_rand32_get() % (max_reachable - min_reachable), where min_reachable = base/2 and max_reachable = 3*base/2 using integer division. When base_reachable_time is 1, both min_reachable and the modulus collapse so the function returns 0, and net_if_ipv6_set_reachable_time() stores that 0 into ipv6->reachable_time. The base_reachable_time is attacker-controlled: handle_ra_input() in subsys/net/ip/ipv6_nbr.c accepts the Reachable Time field of an incoming Router Advertisement whenever it is nonzero and <= MAX_REACHABLE_TIME, so a single unauthenticated, link-local RA carrying a Reachable Time of 1 drives the computed reachable time to 0. Router Advertisements are unauthenticated by default and require only adjacency to the target link. When a neighbor is subsequently confirmed reachable, net_ipv6_nbr_set_reachable_timer() reads the value and executes NET_ASSERT(time, "Zero reachable timeout!"). On builds with CONFIG_ASSERT enabled this triggers a fatal kernel assertion — a remote denial of service; on builds without assertions the reachable timer is armed with K_MSEC(0) and fires immediately, forcing reachable neighbors into perpetual re-solicitation (STALE), degrading Neighbor Discovery. The impact is limited to availability; there is no memory-safety, confidentiality, or integrity consequence.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-15893 since 07/15/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 4.4.2 eliminates this vulnerability. Applying the patch 251079ed50464aa0976eb0738a5afbe009cc9d60 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

• ZephyrProject

Name

• Zephyr

Version

• 4.4.0
• 4.4.1

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CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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