CVE-2026-10653: The Zephyr net_buf library (lib/net_buf/buf.c) manipulated both of its reference counts -- the per-header buf-

Q: How do I fix CVE-2026-10653?

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

Q: Is CVE-2026-10653 being exploited?

CVE-2026-10653 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-2026-10653 affect?

CVE-2026-10653 affects zephyr. Severity is medium (CVSS 6.4). The Zephyr net_buf library (lib/net_buf/buf.c) manipulated both of its reference counts -- the per-header buf->ref and the per-data-block ref_count at the start of each variable/heap data allocation -- with plain non-atomic C operators (buf

Routine

MEDIUM 6.4UPGRADE

CVE-2026-10653 is a medium-severity flaw (CVSS 6.4) affecting zephyr. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The Zephyr net_buf library (lib/net_buf/buf.c) manipulated both of its reference counts -- the per-header buf->ref and the per-data-block ref_count at the start of each variable/heap data allocation -- with plain non-atomic C operators (buf->ref++, if (--buf->ref > 0), if (--(*ref_count))). The API is documented as self-synchronizing: callers may share one buffer across threads (e.g. via k_fifo) and each holder independently calls net_buf_unref(

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.4 (Medium)
Attack vector	Adjacent network
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Weakness	CWE-415
Published	2026-06-30
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

2026-06-30 17:16 UTCPublished CVE record published
2026-10-25 21:10 UTCUpdated Record last modified

zephyrproject zephyr UPGRADE

Affected: >= 2.7.0 and <= 4.4.1

Fixed in: newer than 4.4.1

Safe to downgrade to: a release before 2.7.0

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.

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-2026-10653?

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

Is CVE-2026-10653 being exploited?

CVE-2026-10653 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-2026-10653 affect?

CVE-2026-10653 affects zephyr. Severity is medium (CVSS 6.4). The Zephyr net_buf library (lib/net_buf/buf.c) manipulated both of its reference counts -- the per-header buf->ref and the per-data-block ref_count at the start of each variable/heap data allocation -- with plain non-atomic C operators (buf

How urgent is CVE-2026-10653?

Priority 36/100. Public exploit reference

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References

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