CVE-2026-15893
MEDIUM 6.5net_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.
No known exploitation, public exploit, or elevated probability at this time. Track for changes.
Exploitation likelihood
0.3%chance of exploitation in 30 days · 26th percentile
Impact if exploited
6.5CVSS 3.1 · MEDIUM
- ConfidentialityNone
- IntegrityNone
- AvailabilityHigh
What an attacker needs
- ⚠Access: Must sit on the same / adjacent network
- ✓Privileges: No account or privileges required
- ✓User interaction: No user interaction needed
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept
No public PoC is currently catalogued.
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Data snapshot:
Weakness (CWE)
- CWE-617: dos
CVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References and research data (JSON)
All CVSS metrics
- MEDIUM 6.5 v3.1 · CNA Primary
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - MEDIUM 6.5 v3.1 · NVD Secondary
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
Patches & mitigations
- https://github.com/zephyrproject-rtos/zephyr/commit/251079ed50464aa0976eb0738a5afbe009cc9d60 CVE record · zephyr · Updated 2026-09-14T18:49:55.827Z
NVD · CVE-2026-15893 · Updated 2026-09-14T21:10:41.650
Advisories
- https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-77767 EUVD · EUVD-2026-77767
Technical & other
- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8v32-9xf8-r765CVE record · zephyr · Updated 2026-09-14T18:49:55.827Z
NVD · CVE-2026-15893 · Updated 2026-09-14T21:10:41.650