What’s Vulnerable › Vulnerabilities

CVE-2021-30481

• Severity: critical (CVSS 9.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-04-10 · updated 2026-06-17
• Weakness: CWE-120

Description

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.

Affected products

• Valvesoftware Steam Client: through 2021-04-10

References

• https://news.ycombinator.com/item?id=26762170
• https://twitter.com/floesen_/status/1337107178096881666
• https://twitter.com/the_secret_club/status/1380868759129296900
• https://www.youtube.com/watch?v=rNQn--9xR1Q
• https://news.ycombinator.com/item?id=26762170
• https://twitter.com/floesen_/status/1337107178096881666
• https://twitter.com/the_secret_club/status/1380868759129296900
• https://www.youtube.com/watch?v=rNQn--9xR1Q

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