CVE-2021-22538
Published: 31 March 2021
Summary
CVE-2021-22538 is a medium-severity Improper Input Validation (CWE-20) vulnerability in Google Exposure Notifications Verification Server. Its CVSS base score is 6.3 (Medium).
Operationally, ranked at the 47.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-0963
Vulnerability details
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…
more
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.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Access control policy can specify and enforce secure default permissions for resources.
Guides setting of default permissions to the minimum required level.
Establishes requirements for appropriate default permissions on system resources as part of configuration management.
Baseline establishment and updates on install/upgrade ensure correct default permissions rather than insecure ones.
Requiring the most restrictive settings instead of defaults prevents incorrect default permissions on resources.
Requires documented processes that include setting and maintaining correct default permissions for configuration items.
Requires addressing secure default permissions in physical and environmental protection controls.
Tailoring explicitly overrides or scopes default permission assignments in the baseline to match the system's actual risk and operational needs.