CVE-2026-10686Network attack vector

Denial of service via undecremented IPv6 hop limit

Published Jul 31, 2026 · Updated Jul 31, 2026

Denial of service in Zephyr RTOS 1.8.0 through 4.4.1 allows remote attackers to exhaust forwarding resources through IPv6 routing loops. Both branches of ipv6_route_packet() mark routed unicast packets for forwarding and call net_send_data() without decrementing or expiring the IPv6 hop limit. Reachability requires IPv6 routing through CONFIG_NET_ROUTE, plus CONFIG_NET_ROUTING for cross-interface forwarding, and a transient Layer 3 loop; affected routers then sustain the loop and consume CPU and link bandwidth.

CVSS severity5.8
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Zephyr RTOS 1.8.0 through 4.4.1 allows remote attackers to exhaust forwarding resources through IPv6 routing loops. Both branches of ipv6_route_packet() mark routed unicast packets for forwarding and call net_send_data() without decrementing or expiring the IPv6 hop limit. Reachability requires IPv6 routing through CONFIG_NET_ROUTE, plus CONFIG_NET_ROUTING for cross-interface forwarding, and a transient Layer 3 loop; affected routers then sustain the loop and consume CPU and link bandwidth.

The record

CVE
CVE-2026-10686
Published
Jul 31, 2026
Updated
Jul 31, 2026
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-835, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 31, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 31, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.8.0 <4.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=1.8.0 <4.5.0

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.8Zephyr ProjectCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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