CVE-2026-10686

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 73% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Zephyr's IPv6 forwarding path re-sent routed unicast packets without ever decrementing the IPv6 hop limit. Both routing branches of ipv6_route_packet() (subsys/net/ip) were affected: the explicit-route path (net_route_packet()) and the on-link cross-interface path (net_route_packet_if()). Each set the packet forwarding flag and called net_send_data() with the hop limit untouched and no expiry check.

Per RFC 8200 the hop-limit decrement is the mechanism that bounds packet lifetime and terminates routing loops; without it, a device acting as an IPv6 router relays looping packets indefinitely. An on-path attacker who can induce or exploit a transient L3 loop turns it into a permanent forwarding storm, causing CPU/bandwidth resource exhaustion (availability DoS) on the forwarder and adjacent links; path-discovery and loop diagnostics that rely on hop-limit expiry are also defeated.

Affected configurations. In every affected release the forwarding path is reached via CONFIG_NET_ROUTE (enabled by default when CONFIG_NET_IPV6_NBR_CACHE is set), together with CONFIG_NET_ROUTING for cross-interface routing. Note that CONFIG_NET_IPV6_FORWARDING and CONFIG_NET_IPV4_FORWARDING — which appear in the fix and in this advisory's evidence notes — were introduced after v4.4.0, when the routing options were split and renamed; they do not exist in any affected release. When auditing a v4.4.1-or-earlier configuration, look for CONFIG_NET_ROUTE and CONFIG_NET_ROUTING.

IPv4 is not affected in any release. The IPv4 forwarding path (net_route_ipv4_packet() in route_ipv4.c) was added after v4.4.0 and has never shipped in a release. Its TTL decrement and IPv4 header-checksum recomputation landed on main as part of the same fix, so the evidence notes below discuss it, but no released version is reachable by way of IPv4.

Affected releases are v1.8.0 through v4.4.1: v1.8.0 introduced net_route_packet() and v2.2.0 added net_route_packet_if(), and neither decremented the hop limit. v4.3.1 carries the explicit-route fix but not the on-link one, so it is affected as well. Fixed on main by 7d8f1afa7345 (explicit-route path) and 589eadc74efa (on-link path).

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
38(Track)
EG Risk 38/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
27%
KEV
Not listed

Published

July 31, 2026

Last Modified

August 7, 2026

Advisory Details (2)

Auto-updated Jul 31, 2026
Patch available. Sources: github_commit, github.
github Patch Available

Missing hop-limit decrement on IPv6 forwarding path allows unbounded packet looping (DoS) in Zephyr routers · Advisory · zephyrproject-rtos/zephyr · GitHub

https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-4cg6-6jc4-2r6h
github_commit

commit 7d8f1afa7345 (zephyrproject-rtos/zephyr)

Fix landed in zephyrproject-rtos/zephyr commit 7d8f1afa7345 — awaiting tagged release

https://github.com/zephyrproject-rtos/zephyr/commit/7d8f1afa7345975b58405d6fba18bb8c3f7cb12a

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-25 19:23 UTCEG score recompute
  2. 2026-08-25 13:48 UTCEPSS rescore
  3. 2026-08-24 18:01 UTCEG score recompute
  4. 2026-08-23 03:59 UTCEG score recompute
  5. 2026-08-23 00:19 UTCEPSS rescore
  6. 2026-08-22 02:37 UTCEG score recompute
  7. 2026-08-21 23:48 UTCEPSS rescore
  8. 2026-08-21 00:48 UTCEG score recompute
  9. 2026-08-20 22:55 UTCEPSS rescore
  10. 2026-08-19 23:07 UTCEG score recompute
  11. 2026-08-19 17:03 UTCEPSS rescore
  12. 2026-08-18 21:45 UTCEG score recompute
  13. 2026-08-18 13:48 UTCEPSS rescore
  14. 2026-08-17 20:12 UTCEG score recompute
  15. 2026-08-16 18:50 UTCEG score recompute
  16. 2026-08-16 14:56 UTCEPSS rescore
  17. 2026-08-16 05:58 UTCEG score recompute
  18. 2026-08-16 02:14 UTCEPSS rescore
  19. 2026-08-15 04:37 UTCEG score recompute
  20. 2026-08-15 01:30 UTCEPSS rescore
  21. 2026-08-14 03:16 UTCEG score recompute
  22. 2026-08-13 22:00 UTCEPSS rescore
  23. 2026-08-13 01:54 UTCEG score recompute
  24. 2026-08-12 13:50 UTCEPSS rescore
  25. 2026-08-12 00:33 UTCEG score recompute
Show 23 more
  1. 2026-08-11 13:42 UTCEPSS rescore
  2. 2026-08-11 11:52 UTCEG score recompute
  3. 2026-08-10 23:59 UTCEPSS rescore
  4. 2026-08-09 21:50 UTCEG score recompute
  5. 2026-08-09 13:46 UTCEPSS rescore
  6. 2026-08-08 20:29 UTCEG score recompute
  7. 2026-08-08 16:37 UTCEPSS rescore
  8. 2026-08-07 19:08 UTCEG score recompute▲ 1.70
  9. 2026-08-07 19:07 UTCNVD updateCVSS v3 → 7.5 · severity → HIGH
  10. 2026-08-06 14:46 UTCEG score recompute
  11. 2026-08-06 13:46 UTCEPSS rescore
  12. 2026-08-05 19:17 UTCEPSS rescore
  13. 2026-08-05 14:11 UTCEG score recompute
  14. 2026-08-04 15:09 UTCEPSS rescore
  15. 2026-08-04 12:34 UTCEG score recompute
  16. 2026-08-04 10:38 UTCEPSS rescore
  17. 2026-08-03 20:03 UTCEG score recompute
  18. 2026-08-03 10:35 UTCEPSS rescore
  19. 2026-08-02 19:29 UTCEG score recompute
  20. 2026-08-02 02:26 UTCEPSS rescore
  21. 2026-07-31 18:19 UTCEG score recompute
  22. 2026-07-31 16:21 UTCEG score recompute
  23. 2026-07-31 16:18 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-10686?
CVE-2026-10686 is a high vulnerability published on July 31, 2026. Zephyr's IPv6 forwarding path re-sent routed unicast packets without ever decrementing the IPv6 hop limit. Both routing branches of ipv6routepacket() (subsys/net/ip) were affected: the explicit-route path (netroutepacket()) and the on-link cross-interface path (netroutepacketif()). Each set the…
When was CVE-2026-10686 disclosed?
CVE-2026-10686 was first published in the National Vulnerability Database on July 31, 2026, with the most recent update on August 7, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-10686 actively exploited?
CVE-2026-10686 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 72.8% of all scored CVEs.
What is the CVSS score of CVE-2026-10686?
CVE-2026-10686 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-10686?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-10686, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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