CVE-2026-12631

Kernel crash via inverted syscall verification

Published Aug 18, 2026 · Updated Aug 19, 2026

Authorization error in Zephyr RTOS before 4.4.2 allows local users to crash the kernel via k_thread_join() or k_thread_abort(). In thread_obj_validate() in kernel/thread.c, the access-denied branch passes the nonzero error code ret to K_SYSCALL_VERIFY_MSG, which treats true as success, suppresses K_OOPS, and falls through to CODE_UNREACHABLE instead of terminating the caller. Reachability requires CONFIG_USERSPACE and a user-mode thread that invokes either syscall on an unauthorized thread object; Clang builds crash deterministically, while GCC builds can also bypass the intended authorization check and enter the real thread operation for an unauthorized target.

CVSS severity6.5
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization error in Zephyr RTOS before 4.4.2 allows local users to crash the kernel via k_thread_join() or k_thread_abort(). In thread_obj_validate() in kernel/thread.c, the access-denied branch passes the nonzero error code ret to K_SYSCALL_VERIFY_MSG, which treats true as success, suppresses K_OOPS, and falls through to CODE_UNREACHABLE instead of terminating the caller. Reachability requires CONFIG_USERSPACE and a user-mode thread that invokes either syscall on an unauthorized thread object; Clang builds crash deterministically, while GCC builds can also bypass the intended authorization check and enter the real thread operation for an unauthorized target.

The record

CVE
CVE-2026-12631
Published
Aug 18, 2026
Updated
Aug 19, 2026
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-862, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 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=2.3.0 <4.4.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=2.3.0 <4.4.2

Published CVSS scores

6.5Zephyr ProjectCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

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.

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No observations available

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

Weakness, pattern, technique

CWE-862Missing Authorization
T1068Exploitation for Privilege Escalation

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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