Cyber Resilience

CVE-2021-30481

HighPublic PoC

Published: 10 April 2021

Published
10 April 2021
Modified
03 November 2025
KEV Added
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Patch
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CVSS Score v3.1 8.0 CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H
EPSS Score 0.0691 91.6th percentile
Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-30481 is a high-severity Classic Buffer Overflow (CWE-120) vulnerability in Valvesoftware Steam Client. Its CVSS base score is 8.0 (High).

Operationally, ranked in the top 8.4% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

EU & UK References

Vulnerability details

Valve Steam before 2021-04-17, when a Source engine game is installed, allows remote authenticated users to execute arbitrary code because of a buffer overflow that occurs for a Steam invite after one click.

CWE(s)
CWE-120

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

valvesoftware
steam client
≤ 2021-04-10

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.

SC-27 Platform-independent Applications
addresses: CWE-120

Platform-independent managed code eliminates the need for unchecked native buffer copies that are the root cause of classic buffer overflows.

References