CVE-2021-36133

TrustZone bypass via unset CSU access policy

Published Dec 7, 2021 · Updated Aug 4, 2024

TrustZone bypass in all OP-TEE OS releases supporting NXP i.MX devices allows local users to read and write Secure World memory via DMA. The CSU driver leaves csu_sa_setting null for several i.MX6 and i.MX7 targets, so Security Access register defaults mark DMA-capable peripherals as Secure. Code already executing in the Normal World can direct an accessible bus master at Secure World memory, defeating TEE confidentiality and integrity; upstream disputes that the open reference configuration is itself a security defect.

CVSS severity7.1
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

TrustZone bypass in all OP-TEE OS releases supporting NXP i.MX devices allows local users to read and write Secure World memory via DMA. The CSU driver leaves csu_sa_setting null for several i.MX6 and i.MX7 targets, so Security Access register defaults mark DMA-capable peripherals as Secure. Code already executing in the Normal World can direct an accessible bus master at Secure World memory, defeating TEE confidentiality and integrity; upstream disputes that the open reference configuration is itself a security defect.

The record

CVE
CVE-2021-36133
Published
Dec 7, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-732, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.1NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
3.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-732Incorrect Permission Assignment for Critical Resource
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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