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» CVE-2021-30481
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.
NVD Status： Modified ，CVE State: published
Threat Intelligence & Risk Assessment for CVE-2021-30481
Conclusion & alert: CVE-2021-30481 is rated High Exploit Risk (78.4/100) : CVSS High severity, with high exploitation likelihood (EPSS 6.91%, 91th percentile).Core evidence: 2 public exploit reference(s) are indexed (Exploit-DB).Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
Public exploit references (Exploit-DB) for CVE-2021-30481
Exploit prediction scoring system (EPSS) score for CVE-2021-30481
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
#
Date
Old EPSS score
New EPSS score
Delta (New - Old)
1
2026-05-10
7.50%
6.91%
-0.60%
2
2026-04-12
7.68%
7.50%
-0.18%
3
2026-04-01
—
7.68%
—
Full EPSS history
(25 records total)
Common vulnerability scoring system (CVSS) metrics for CVE-2021-30481
CVSS metrics for this CVE.
Base score
Version
Severity
Vector
Exploitability
Impact
Score source
8.0
3.1
HIGH
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H
Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
1.3
6.0
[email protected]
9.0
3.1
CRITICAL
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
2.3
6.0
[email protected]
6.0
2.0
MEDIUM
AV:N/AC:M/Au:S/C:P/I:P/A:P
Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
6.8
6.4
[email protected]
Weakness enumeration for CVE-2021-30481
Affected software / configurations for CVE-2021-30481
References for CVE-2021-30481
cvelogic
Threat Intelligence