{"id":"CVE-2026-15893","summary":"Zephyr IPv6 Neighbor Discovery zero reachable time from crafted Router Advertisement causes assertion/DoS","details":"net_if_ipv6_calc_reachable_time() in subsys/net/ip/net_if.c derives a randomized ND reachable time from ipv6-\u003ebase_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-\u003ereachable_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 \u003c= 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.","aliases":["GHSA-8v32-9xf8-r765"],"modified":"2026-09-16T08:29:35.685600Z","published":"2026-09-14T18:49:55.827Z","database_specific":{"cna_assigner":"zephyr","cwe_ids":["CWE-617"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/15xxx/CVE-2026-15893.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/15xxx/CVE-2026-15893.json"},{"type":"ADVISORY","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8v32-9xf8-r765"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-15893"},{"type":"FIX","url":"https://github.com/zephyrproject-rtos/zephyr/commit/251079ed50464aa0976eb0738a5afbe009cc9d60"},{"type":"PACKAGE","url":"https://github.com/zephyrproject-rtos/zephyr"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/zephyrproject-rtos/zephyr","events":[{"introduced":"bdc3107d5c47d9cf4b6a4e948186a0a2730d92c5"},{"fixed":"251079ed50464aa0976eb0738a5afbe009cc9d60"}],"database_specific":{"extracted_events":[{"introduced":"1.7.0"},{"fixed":"4.4.2"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"database_specific":{"vanir_signatures":[{"source":"https://github.com/zephyrproject-rtos/zephyr/commit/251079ed50464aa0976eb0738a5afbe009cc9d60","target":{"file":"subsys/net/ip/net_if.c","function":"net_if_ipv6_calc_reachable_time"},"deprecated":false,"digest":{"length":319,"function_hash":"182681815047846322431475769106410366799"},"id":"CVE-2026-15893-1f577ae1","signature_type":"Function","signature_version":"v1"},{"target":{"file":"subsys/net/ip/net_if.c"},"deprecated":false,"digest":{"line_hashes":["62456918687243599427324157859222429331","180364764747878106792660337274722553555","45857866936001433803126987754033211369","266130666490979423480821628237437534232","132482748126583528675940258433982398404","145518796618002063109932855948724647631","234421704542647271396025410894190203337","222538889391292852128983690784163325260","131104435943552725386414307920383595640","151544482934419177424503270952855184674","129557033610055631872993883967123735944","277103191223392816432180832419759599112"],"threshold":0.9},"id":"CVE-2026-15893-97178f54","signature_type":"Line","signature_version":"v1","source":"https://github.com/zephyrproject-rtos/zephyr/commit/251079ed50464aa0976eb0738a5afbe009cc9d60"}],"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-15893.json","vanir_signatures_modified":"2026-09-16T08:29:35Z"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}