CVE-2026-10666: parse_ipv4() in subsys/net/ip/utils.c (reached via net_ipaddr_parse() for strings of the form "a.b.c.d:port")

Q: How do I fix CVE-2026-10666?

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

Q: Is CVE-2026-10666 being exploited?

CVE-2026-10666 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-2026-10666 affect?

CVE-2026-10666 affects zephyr. Severity is high (CVSS 8.1). parse_ipv4() in subsys/net/ip/utils.c (reached via net_ipaddr_parse() for strings of the form "a.b.c.d:port") copies the port substring into a fixed 17-byte stack buffer (char ipaddr[NET_IPV4_ADDR_LEN + 1]) using a length of str_len - end -

Q: How urgent is CVE-2026-10666?

Priority 51/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 8.1REMOTEUPGRADE

CVE-2026-10666 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.

parse_ipv4() in subsys/net/ip/utils.c (reached via net_ipaddr_parse() for strings of the form "a.b.c.d:port") copies the port substring into a fixed 17-byte stack buffer (char ipaddr[NET_IPV4_ADDR_LEN + 1]) using a length of str_len - end - 1, where str_len is the full, unbounded input length and end is only the (<=15-byte) offset of the ':' delimiter. Because the destination size is never consulted, a crafted address string with a long suffix af

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 49%)
CISA exploited list	No
Weakness	CWE-121
Published	2026-07-12
Last modified	2026-10-24

Publisher (CNA): Zephyr Project · Vendor: zephyrproject

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-12 17:16 UTCPublished CVE record published
2026-10-24 22:10 UTCUpdated Record last modified

zephyrproject zephyr UPGRADE

Affected: >= 1.9.0 and <= 4.4.1

Fixed in: newer than 4.4.1

Safe to downgrade to: a release before 1.9.0

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.

Exact fixes by distribution

Fedora 46 · conda · FIXED · 26.9.4-2.fc46 · FEDORA-2026-09931756f1 · source

sudo dnf upgrade --advisory=FEDORA-2026-09931756f1

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-532c-7g7f-jhmh

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-2026-10666?

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

Is CVE-2026-10666 being exploited?

CVE-2026-10666 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-2026-10666 affect?

CVE-2026-10666 affects zephyr. Severity is high (CVSS 8.1). parse_ipv4() in subsys/net/ip/utils.c (reached via net_ipaddr_parse() for strings of the form "a.b.c.d:port") copies the port substring into a fixed 17-byte stack buffer (char ipaddr[NET_IPV4_ADDR_LEN + 1]) using a length of str_len - end -

How urgent is CVE-2026-10666?

Priority 51/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

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References

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