CVE-2021-39993Public exploit

EL3 code execution via mutable log header

Published Jan 7, 2022 · Updated Aug 4, 2024

Memory corruption in Huawei Secure Monitor on EMUI 11.0.0 and Magic UI 4.0.0 allows local users with kernel control to execute code at EL3. The HISEE log path trusts the mutable addr field in a kernel-shared hlog_header after validation, so later log copies write to attacker-chosen secure-memory addresses. Exploitation begins from a compromised Android kernel and grants control of the device's highest exception level.

CVSS severity9.8
Critical
EPSS probability0.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Huawei Secure Monitor on EMUI 11.0.0 and Magic UI 4.0.0 allows local users with kernel control to execute code at EL3. The HISEE log path trusts the mutable addr field in a kernel-shared hlog_header after validation, so later log copies write to attacker-chosen secure-memory addresses. Exploitation begins from a compromised Android kernel and grants control of the device's highest exception level.

The record

CVE
CVE-2021-39993
Published
Jan 7, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-190, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Jan 7, 2022CVE 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 privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8National Institute of Standards and TechnologyCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5National Institute of Standards and TechnologyAV:N/AC:L/Au:N/C:P/I:P/A:P

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1068Exploitation for Privilege Escalation

Public exploit references

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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