CVE-2026-7656: The IPv6 Neighbor Discovery handlers in subsys/net/ip/ipv6_nbr.c (handle_ra_input, handle_ns_input, handle_na_

Q: How do I fix CVE-2026-7656?

zephyr: upgrade to newer than 4.4.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-7656 being exploited?

CVE-2026-7656 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-7656 affect?

CVE-2026-7656 affects zephyr. Severity is high (CVSS 8.1). The IPv6 Neighbor Discovery handlers in subsys/net/ip/ipv6_nbr.c (handle_ra_input, handle_ns_input, handle_na_input) used an incorrect boolean expression that combined the RFC 4861 validity checks with the ICMPv6 code check using the wrong

Q: How urgent is CVE-2026-7656?

Priority 40/100. High severity; Public exploit reference

This month

HIGH 8.1UPGRADE

CVE-2026-7656 is a high-severity flaw (CVSS 8.1) affecting zephyr. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The IPv6 Neighbor Discovery handlers in subsys/net/ip/ipv6_nbr.c (handle_ra_input, handle_ns_input, handle_na_input) used an incorrect boolean expression that combined the RFC 4861 validity checks with the ICMPv6 code check using the wrong operator precedence: the form was ((length/hop/source/target checks) && (icmp_hdr->code != 0)). Because every legitimate ND message carries ICMPv6 code 0, an attacker setting code == 0 (the normal value) caused

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Adjacent network
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 74%)
CISA exploited list	No
Weakness	CWE-290, CWE-670
Published	2026-06-29
Last modified	2026-10-25

Publisher (CNA): Zephyr Project · Vendor: zephyrproject

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-29 23:16 UTCPublished CVE record published
2026-10-25 21:10 UTCUpdated Record last modified

zephyrproject zephyr UPGRADE

Affected: <= 4.4.1

Fixed in: newer than 4.4.1

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-7656?

zephyr: upgrade to newer than 4.4.1. Exact commands for each OS are on this page.

Is CVE-2026-7656 being exploited?

CVE-2026-7656 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-7656 affect?

CVE-2026-7656 affects zephyr. Severity is high (CVSS 8.1). The IPv6 Neighbor Discovery handlers in subsys/net/ip/ipv6_nbr.c (handle_ra_input, handle_ns_input, handle_na_input) used an incorrect boolean expression that combined the RFC 4861 validity checks with the ICMPv6 code check using the wrong

How urgent is CVE-2026-7656?

Priority 40/100. High severity; Public exploit reference

Related CVEs

CVE-2026-13351 HIGH 7.5 UPGRADE Zephyr's IPv6 network stack can be prevented from receiving or processing future incoming packets by sending a
CVE-2026-8023 HIGH 7.5 UPGRADE Zephyr's HTTP server (subsys/net/lib/http) provides a static-filesystem resource type (HTTP_RESOURCE_TYPE_STAT
CVE-2026-10655 MEDIUM 6.5 UPGRADE The asynchronous SNTP client in Zephyr (subsys/net/lib/sntp/sntp.c, sntp_close_async) closed the UDP socket fi
CVE-2026-10652 MEDIUM 4.8 UPGRADE Zephyr's DNS resolver (subsys/net/lib/dns) parses resource records from DNS responses in dns_unpack_answer(),
CVE-2026-10653 MEDIUM 6.4 UPGRADE The Zephyr net_buf library (lib/net_buf/buf.c) manipulated both of its reference counts -- the per-header buf-

References

← Back to latest CVEs