{"id":"CVE-2026-15893","title":"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…","summary":"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…","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-617"],"vendor":"zephyrproject","product":"zephyr","affected":["zephyr >= 1.7.0 < 4.4.2"],"published":"2026-09-14","updated":"2026-09-14","sourceUpdated":"2026-09-14T21:10:41.650","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-15893","references":[{"url":"https://github.com/zephyrproject-rtos/zephyr/commit/251079ed50464aa0976eb0738a5afbe009cc9d60","label":"vulnerabilities@zephyrproject.org"},{"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8v32-9xf8-r765","label":"vulnerabilities@zephyrproject.org"}],"tags":["nvd","cve.org"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-09-14T19:02:33.869630Z"},"ingestedAt":"2026-09-14T19:13:23.468Z","epss":0.002,"epssPercentile":0.10171,"slug":"CVE-2026-15893","body":"## Overview\n\nnet_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.\n\nThe 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.\n\nWhen 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}