CVE-2021-22538Network attack vector

Privilege escalation via unknown permission bitmask

Published Mar 31, 2021 · Updated Aug 3, 2024

Privilege escalation in Google Exposure Notifications Verification Server before 0.23.1 allows remote authenticated users to create privileged users. CompileAndAuthorize accepts unknown numeric permissions that pass its bitwise AND check, then combines them with OR to set unauthorized privilege bits. Exploitation requires UserWrite permission and a crafted request or malicious proxy; the resulting user-creation event is recorded in the Event Log.

CVSS severity6.3
Medium
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privilege escalation in Google Exposure Notifications Verification Server before 0.23.1 allows remote authenticated users to create privileged users. CompileAndAuthorize accepts unknown numeric permissions that pass its bitwise AND check, then combines them with OR to set unauthorized privilege bits. Exploitation requires UserWrite permission and a crafted request or malicious proxy; the resulting user-creation event is recorded in the Event Log.

The record

CVE
CVE-2021-22538
Published
Mar 31, 2021
Updated
Aug 3, 2024
Vendor
Google
Product
Exposure Notifications Verification Server
Classifications
CWE-269, CWE-276, CWE-20, T1136
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 31, 2021CVE 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=stable <=0.23.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Google · Exposure Notifications Verification Serverversion=stable <=0.23.0

Published CVSS scores

6.3Google Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDAV:N/AC:L/Au:S/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.

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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-269Improper Privilege Management
CWE-276Incorrect Default Permissions
CWE-20Improper Input Validation
T1136Create Account

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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