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CVE-2021-30481

31
FAUCET Score

CVE-2021-30481 is a critical buffer overflow vulnerability affecting Valve Steam clients prior to April 17, 2021, specifically when a Source engine game is installed. This flaw allows remote authenticated attackers to execute arbitrary code with a single click on a malicious Steam invite. Rated 9.0 Critical (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H), it indicates a network-based attack with low complexity and high impact on confidentiality, integrity, and availability. While not listed in CISA KEV or having public Metasploit/Nuclei exploits, its high FAUCET Risk Score of 95/100, significant community discussion (more than 99% of all CVEs), and media coverage suggest considerable attention and potential for exploitation.

Impacted Technologies

VendorProductVersion(s)CPE
<= 2021-04-10CPE matchmatch criteria
cpe:2.3:a:valvesoftware:steam_client:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.0HIGH

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.3
Impact Score
6.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
3.50%
Probability of exploitation in next 30 days
EPSS Percentile
88.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.0350 is in the 94th percentile among its peer group of 265 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.6 Bluesky, 0.3 Mastodon, and 1.6 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

news.ycombinator.com / item
Issue TrackingThird Party Advisory
twitter.com / floesen_/status/1337107178096881666
Third Party Advisory
twitter.com / the_secret_club/status/1380868759129296900
ExploitThird Party Advisory
youtube.com / watch
ExploitThird Party Advisory