CVE-2025-9408

Kernel privilege escalation via mutable syscall return frame

Published Nov 11, 2025 · Updated Nov 12, 2025

Privilege context switching error in Zephyr RTOS 4.2 and earlier allows local users to gain kernel privileges on Cortex-M systems. The syscall entry path clears nPRIV before returning through an exception frame on an attacker-writable thread stack, letting a racing thread replace the saved PC. Exploitation requires Zephyr userspace, repeated low-priority syscalls, and higher-priority preemption before the privileged-stack switch.

CVSS severity8.1
High
EPSS probability0.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privilege context switching error in Zephyr RTOS 4.2 and earlier allows local users to gain kernel privileges on Cortex-M systems. The syscall entry path clears nPRIV before returning through an exception frame on an attacker-writable thread stack, letting a racing thread replace the saved PC. Exploitation requires Zephyr userspace, repeated low-priority syscalls, and higher-priority preemption before the privileged-stack switch.

The record

CVE
CVE-2025-9408
Published
Nov 11, 2025
Updated
Nov 12, 2025
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-270, T1068
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 11, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 12, 2025Record 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=* <=4.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=* <=4.2

Published CVSS scores

8.1Zephyr ProjectCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-270Privilege Context Switching Error
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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