CVE-2021-22566

Execute-restriction bypass via incorrect UXN and PXN bits

Published Jan 18, 2022 · Updated Aug 3, 2024

Permission error in Google Fuchsia before commit 7d731b4e9599088ac3073956933559da7bca6a00 allows local users to bypass execute restrictions. The ARM64 mmu_flags_to_s1_pte_attr function assigns UXN and PXN bits without separating user-executable pages from privileged-executable pages. Local code execution is required; the bypass weakens kernel and user-page execute protections but does not itself provide privilege escalation or service interruption.

CVSS severity5.1
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Permission error in Google Fuchsia before commit 7d731b4e9599088ac3073956933559da7bca6a00 allows local users to bypass execute restrictions. The ARM64 mmu_flags_to_s1_pte_attr function assigns UXN and PXN bits without separating user-executable pages from privileged-executable pages. Local code execution is required; the bypass weakens kernel and user-page execute protections but does not itself provide privilege escalation or service interruption.

The record

CVE
CVE-2021-22566
Published
Jan 18, 2022
Updated
Aug 3, 2024
Vendor
Google
Product
Fuchsia
Classifications
CWE-732, CWE-275, T1211
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 18, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0
  2. Affected versionversion=0 <7d731b4e9599088ac3073956933559da7bca6a00

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Google · Fuchsiaversion=0; version=0 <7d731b4e9599088ac3073956933559da7bca6a00

Published CVSS scores

9.8NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NISTAV:N/AC:L/Au:N/C:P/I:P/A:P
5.1Google Inc.CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA: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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-732Incorrect Permission Assignment for Critical Resource
CWE-275Permission Issues
T1211Exploitation for Defense Evasion

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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