CVE-2021-30481

CRITICALNVD 8.09.0▲
EchelonGraph scoreMEDIUM confidence

Score 9.0 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-24. NVD baseline CVSS 8.0; sources differ by 1.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Elevated
9.0EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 4%CVSS: 8.0Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
8.0
EG Score
9.0(medium)
EG Risk
61(Track*)
EG Risk 61/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity90% × 45%
Exploitation40% × 40%
Automatability30% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
4%
EPSS %ILE
89%
KEV
Not listed

Published

April 10, 2021

Last Modified

November 3, 2025

Advisory Details (4)

Auto-updated Sep 20, 2026
⚠️ Active exploitation confirmed. No patch confirmed yet.
generic
https://www.youtube.com/watch?v=rNQn--9xR1Q
generic

secret club on X: "Two years ago, secret club member @floesen_ reported a remote code execution flaw affecting all source engine games. It can be triggered through a Steam invite. This has yet to be patched, and Valve is preventing us from publicly disclosing it." / X

https://twitter.com/the_secret_club/status/1380868759129296900
generic

🤷‍♂️ on X: "Recently, I've seen some people complaining about long response times at bugbounty programs. Let's play a game, can you beat one of my "recent" gems? A wormable, single click RCE affecting every Steam user that owns atleast one Source engine game - NOT resolved for 500+ days." / X

https://twitter.com/floesen_/status/1337107178096881666
generic🔴 Active Exploitation

Valve accused of ignoring existing RCE vulnerability in Source games for 2 years | Hacker News

https://news.ycombinator.com/item?id=26762170

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 28× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 156 total refreshes for this CVE.

  1. 2026-09-19 15:37 UTCEPSS rescore
  2. 2026-09-18 19:23 UTCEPSS rescore
  3. 2026-09-17 19:23 UTCEPSS rescore
  4. 2026-09-17 19:23 UTCEPSS rescore
  5. 2026-09-16 14:05 UTCEPSS rescore
  6. 2026-09-15 03:06 UTCEPSS rescore
  7. 2026-09-15 03:06 UTCEPSS rescore
  8. 2026-09-12 14:57 UTCEPSS rescore
  9. 2026-09-11 14:49 UTCEPSS rescore
  10. 2026-09-11 09:33 UTCEPSS rescore
  11. 2026-09-08 21:56 UTCEPSS rescore
  12. 2026-09-07 15:58 UTCEPSS rescore
  13. 2026-09-06 13:44 UTCEPSS rescore
  14. 2026-09-05 15:25 UTCEPSS rescore
  15. 2026-09-04 13:57 UTCEPSS rescore
  16. 2026-09-04 05:03 UTCEPSS rescore
  17. 2026-09-04 05:03 UTCEPSS rescore
  18. 2026-09-02 14:08 UTCEPSS rescore
  19. 2026-09-01 13:50 UTCEPSS rescore
  20. 2026-09-01 03:32 UTCEPSS rescore
  21. 2026-08-30 19:14 UTCEPSS rescore
  22. 2026-08-30 01:19 UTCEPSS rescore
  23. 2026-08-28 21:37 UTCEPSS rescore
  24. 2026-08-27 14:22 UTCEPSS rescore
  25. 2026-08-26 14:42 UTCEPSS rescore
Show 75 more
  1. 2026-08-25 13:45 UTCEPSS rescore
  2. 2026-08-24 14:12 UTCEPSS rescore
  3. 2026-08-23 00:16 UTCEPSS rescore
  4. 2026-08-21 23:46 UTCEPSS rescore
  5. 2026-08-20 22:52 UTCEPSS rescore
  6. 2026-08-19 17:01 UTCEPSS rescore
  7. 2026-08-18 13:45 UTCEPSS rescore
  8. 2026-08-17 13:44 UTCEPSS rescore
  9. 2026-08-16 14:53 UTCEPSS rescore
  10. 2026-08-16 02:11 UTCEPSS rescore
  11. 2026-08-16 02:11 UTCEPSS rescore
  12. 2026-08-15 01:27 UTCEPSS rescore
  13. 2026-08-13 21:57 UTCEPSS rescore
  14. 2026-08-12 13:47 UTCEPSS rescore
  15. 2026-08-11 13:38 UTCEPSS rescore
  16. 2026-08-09 13:43 UTCEPSS rescore
  17. 2026-08-08 16:33 UTCEPSS rescore
  18. 2026-08-07 16:23 UTCEPSS rescore
  19. 2026-08-06 13:43 UTCEPSS rescore
  20. 2026-08-05 19:14 UTCEPSS rescore
  21. 2026-08-04 15:06 UTCEPSS rescore
  22. 2026-08-04 10:34 UTCEPSS rescore
  23. 2026-08-03 10:33 UTCEPSS rescore
  24. 2026-08-02 02:24 UTCEPSS rescore
  25. 2026-08-01 04:13 UTCEPSS rescore
  26. 2026-07-30 16:25 UTCEPSS rescore
  27. 2026-07-30 16:25 UTCEPSS rescore
  28. 2026-07-30 01:28 UTCEPSS rescore
  29. 2026-07-30 01:27 UTCEPSS rescore
  30. 2026-07-28 15:33 UTCEPSS rescore
  31. 2026-07-26 14:52 UTCEPSS rescore
  32. 2026-07-26 14:52 UTCEPSS rescore
  33. 2026-07-25 14:15 UTCEPSS rescore
  34. 2026-07-24 14:15 UTCEPSS rescore
  35. 2026-07-23 14:16 UTCEPSS rescore
  36. 2026-07-23 02:00 UTCEG score recompute
  37. 2026-07-22 22:47 UTCEG score recompute
  38. 2026-07-22 14:06 UTCEPSS rescore
  39. 2026-07-22 14:06 UTCEPSS rescore
  40. 2026-07-21 15:22 UTCEPSS rescore
  41. 2026-07-21 15:22 UTCEPSS rescore
  42. 2026-07-20 17:05 UTCEPSS rescore
  43. 2026-07-19 14:28 UTCEPSS rescore
  44. 2026-07-19 02:27 UTCEPSS rescore
  45. 2026-07-19 02:27 UTCEPSS rescore
  46. 2026-07-18 10:02 UTCEPSS rescore
  47. 2026-07-18 10:02 UTCEPSS rescore
  48. 2026-07-16 17:00 UTCEPSS rescore
  49. 2026-07-15 16:55 UTCEPSS rescore
  50. 2026-07-15 16:55 UTCEPSS rescore
  51. 2026-07-15 01:58 UTCEPSS rescore
  52. 2026-07-13 22:27 UTCEPSS rescore
  53. 2026-07-13 22:27 UTCEPSS rescore
  54. 2026-07-13 06:10 UTCEPSS rescore
  55. 2026-07-12 05:44 UTCEPSS rescore
  56. 2026-07-12 05:44 UTCEPSS rescore
  57. 2026-07-11 08:25 UTCEPSS rescore
  58. 2026-07-11 08:25 UTCEPSS rescore
  59. 2026-07-09 19:07 UTCEPSS rescore
  60. 2026-07-08 15:12 UTCEPSS rescore
  61. 2026-07-06 16:25 UTCEPSS rescore
  62. 2026-07-06 16:25 UTCEPSS rescore
  63. 2026-07-06 02:21 UTCEPSS rescore
  64. 2026-07-06 02:21 UTCEPSS rescore
  65. 2026-07-05 02:28 UTCEPSS rescore
  66. 2026-07-04 06:29 UTCEPSS rescore
  67. 2026-07-04 06:29 UTCEPSS rescore
  68. 2026-07-02 16:57 UTCEPSS rescore
  69. 2026-07-01 15:03 UTCEPSS rescore
  70. 2026-06-30 23:20 UTCEPSS rescore
  71. 2026-06-30 23:20 UTCEPSS rescore
  72. 2026-06-29 14:04 UTCEPSS rescore
  73. 2026-06-28 14:05 UTCEPSS rescore
  74. 2026-06-28 04:54 UTCEPSS rescore
  75. 2026-06-28 04:54 UTCEPSS rescore

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCfloesen/CVE-2021-30481
    First seen Apr 17, 2021

    https://nvd.nist.gov/vuln/detail/CVE-2021-30481

    Open source ↗

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-30481?
CVE-2021-30481 is a critical vulnerability published on April 10, 2021. 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.
When was CVE-2021-30481 disclosed?
CVE-2021-30481 was first published in the National Vulnerability Database on April 10, 2021, with the most recent update on November 3, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-30481 actively exploited?
CVE-2021-30481 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 4% probability of exploitation in the next 30 days, which ranks it in the top 11.4% of all scored CVEs.
What is the CVSS score of CVE-2021-30481?
CVE-2021-30481 has a CVSS v3 base score of 8.0 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
How do I remediate CVE-2021-30481?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-30481, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2021-30481

Explore →

Is Your Infrastructure Affected by CVE-2021-30481?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs