CVE-2026-10681: In Zephyr's userspace dynamic-objects subsystem, thread_idx_alloc() in kernel/userspace/userspace.c allocated

Q: How do I fix CVE-2026-10681?

zephyr: upgrade to 4.5.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-10681 being exploited?

CVE-2026-10681 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-2026-10681 affect?

CVE-2026-10681 affects zephyr. Severity is medium (CVSS 6.5). In Zephyr's userspace dynamic-objects subsystem, thread_idx_alloc() in kernel/userspace/userspace.c allocated a new thread permission index from the global _thread_idx_map[] bitmap without holding lists_lock. On SMP systems, two user-mode

Q: How urgent is CVE-2026-10681?

Priority 28/100. Public exploit reference

Routine

MEDIUM 6.5UPGRADE

CVE-2026-10681 is a medium-severity flaw (CVSS 6.5) affecting zephyr. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In Zephyr's userspace dynamic-objects subsystem, thread_idx_alloc() in kernel/userspace/userspace.c allocated a new thread permission index from the global _thread_idx_map[] bitmap without holding lists_lock. On SMP systems, two user-mode threads invoking the k_object_alloc(K_OBJ_THREAD) syscall concurrently can both observe the same low free bit, perform the same non-atomic RMW to clear it, and return the identical tidx. The two newly created

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.1% (top 99%)
CISA exploited list	No
Weakness	CWE-362
Published	2026-07-25
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

2026-07-25 14:16 UTCPublished CVE record published
2026-10-24 13:10 UTCUpdated Record last modified

zephyrproject zephyr UPGRADE

Affected: >= 2.0.0 and < 4.5.0

Fixed in: 4.5.0

Safe to downgrade to: a release before 2.0.0

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-2026-10681?

zephyr: upgrade to 4.5.0. Exact commands for each OS are on this page.

Is CVE-2026-10681 being exploited?

CVE-2026-10681 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-2026-10681 affect?

CVE-2026-10681 affects zephyr. Severity is medium (CVSS 6.5). In Zephyr's userspace dynamic-objects subsystem, thread_idx_alloc() in kernel/userspace/userspace.c allocated a new thread permission index from the global _thread_idx_map[] bitmap without holding lists_lock. On SMP systems, two user-mode

How urgent is CVE-2026-10681?

Priority 28/100. Public exploit reference

Related CVEs

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References

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