How severe is CVE-2021-22538?

CVE-2021-22538 has a CVSS 3.x base score of 6.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2021-22538 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-22538?

CVE-2021-22538 affects Google Exposure Notifications Verification Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-22538?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-22538 published?

CVE-2021-22538 was published on 2021-03-31 and last updated on 2026-06-17.

CVE-2021-22538

CVE-2021-22538 is a medium-severity vulnerability in Google Exposure Notifications Verification Server with a CVSS 3.x base score of 6.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-276.

Key facts

Severity: Medium (CVSS 3.x base score 6.3)
CVSS v2: 6.5
EPSS exploit prediction: 1% (49th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-276
Affected product: Google Exposure Notifications Verification Server
Published: 2021-03-31
Last modified: 2026-06-17

Description

A privilege escalation vulnerability impacting the Google Exposure Notification Verification Server (versions prior to 0.23.1), allows an attacker who (1) has UserWrite permissions and (2) is using a carefully crafted request or malicious proxy, to create another user with higher privileges than their own. This occurs due to insufficient checks on the allowed set of permissions. The new user creation event would be captured in the Event Log.

Frequently asked questions

What is CVE-2021-22538?: A privilege escalation vulnerability impacting the Google Exposure Notification Verification Server (versions prior to 0.23.1), allows an attacker who (1) has UserWrite permissions and (2) is using a carefully crafted request or malicious proxy, to create another user with higher privileges than their own. This occurs due to insufficient checks on the allowed set of permissions. The new user creation event would be captured in the Event Log.
How severe is CVE-2021-22538?: CVE-2021-22538 has a CVSS 3.x base score of 6.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2021-22538 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-22538?: CVE-2021-22538 affects Google Exposure Notifications Verification Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-22538?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-22538 published?: CVE-2021-22538 was published on 2021-03-31 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:google:exposure_notifications_verification_server:*:*:*:*:*:*:*:*

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