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.
CVE-2021-30481
“▲” beside the score: it is higher than NVD's CVSS score.
Score 9.0 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-24. NVD baseline CVSS 8.0; sources differ by 1.0.
Also known asEUVD-2021-17404 (ENISA EUVD) · GHSA-3jx7-82j9-5prx (GitHub Security Advisories)Source: ENISA EUVD
- Public exploit or proof-of-concept code is available
No fix has been recorded since the CVE record was published in 2021 — if the vendor still supports the product, apply the fixed version it names; if not, isolate the affected system (restrict network access to it, for example with a firewall, or keep it off the internet) or retire the product.
- CVSS v3
- 8.0
- EG Score
- 9.0CRITICALmedium confidence
- EG Risk
- 57EG Risk 57/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity90% × 45%Impact severity (EG Severity): CVSS 9.0 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation40% × 40%EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.Automatability0% × 15%CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.Exploitation public PoC (exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: No fix has been recorded since the CVE record was published in 2021. If the vendor still supports the product, apply the fixed version it names within your standard update timelines at low or medium mission impact and sooner than that at high; if it no longer does, isolate the affected system (restrict network access to it, for example with a firewall, or keep it off the internet) on your normal schedule at low or medium mission impact and sooner than that at high, or retire the product. - EPSS PROB
- 3.5%
- EPSS %ILE
- 89th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (9.0): severity, escalated by confirmed exploitation. This CVE's 9.0 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.0 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 3.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-02). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track* at medium mission impactTrack at low, Track* at medium and Attend at high mission impact.CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.
No fix has been recorded since the CVE record was published in 2021. If the vendor still supports the product, apply the fixed version it names within your standard update timelines at low or medium mission impact and sooner than that at high; if it no longer does, isolate the affected system (restrict network access to it, for example with a firewall, or keep it off the internet) on your normal schedule at low or medium mission impact and sooner than that at high, or retire the product.
Exploitation public PoC (exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
April 10, 2021
Last Modified
November 3, 2025
Advisory Details (4)
Auto-updated Sep 20, 2026secret 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🤷♂️ 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/1337107178096881666Valve accused of ignoring existing RCE vulnerability in Source games for 2 years | Hacker News
https://news.ycombinator.com/item?id=26762170Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 22× in last 7d / 73× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 96 of 240 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 4 repeat rows among the latest 100 are merged into the row they repeat. The 144 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-02 21:04 UTCEG score recompute
- 2026-11-02 21:04 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-11-02 16:37 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-11-01 21:47 UTCEG score recompute
- 2026-11-01 21:47 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-31 22:29 UTCEG score recompute
- 2026-10-31 22:29 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-31 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-30 23:12 UTCEG score recompute
- 2026-10-30 23:12 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-30 16:29 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-29 23:55 UTCEG score recompute
- 2026-10-29 23:55 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-29 16:29 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-29 00:38 UTCEG score recompute
- 2026-10-29 00:38 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-28 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-28 01:19 UTCEG score recompute
- 2026-10-28 01:19 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-27 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-27 01:57 UTCEG score recompute
- 2026-10-27 01:57 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-26 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-25 22:40 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-25 18:29 UTCEG score recompute
Show 71 moreShow fewer
- 2026-10-25 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-24 23:22 UTCEG score recompute
- 2026-10-24 23:22 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-24 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-24 00:05 UTCEG score recompute
- 2026-10-24 00:05 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-23 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-23 00:46 UTCEG score recompute
- 2026-10-23 00:46 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-22 16:29 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-22 01:26 UTCEG score recompute
- 2026-10-22 01:25 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-21 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-21 02:06 UTCEG score recompute
- 2026-10-21 02:05 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-20 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-20 02:47 UTCEG score recompute
- 2026-10-20 02:47 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-19 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-19 02:36 UTCEG score recompute
- 2026-10-19 02:36 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-18 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-18 03:17 UTCEG score recompute
- 2026-10-18 03:16 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-17 16:28 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-17 03:56 UTCEG score recompute
- 2026-10-17 03:55 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-16 16:33 UTCEPSS rescoreEPSS 3.5% · 89th percentile
- 2026-10-16 04:34 UTCEG score recompute
- 2026-10-16 04:34 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-15 16:28 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-15 03:01 UTCEG score recompute
- 2026-10-15 03:00 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-14 16:28 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-13 23:12 UTCEG score recompute
- 2026-10-13 23:11 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-13 16:28 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-12 19:18 UTCGHSA enrichmentGHSA-3jx7-82j9-5prx · GitHub severity CRITICAL · GitHub CVSS 9.0
- 2026-10-12 19:18 UTCEG score recompute
- 2026-10-12 16:29 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-11 23:43 UTCEG score recompute
- 2026-10-11 13:43 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-10 19:56 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-09 20:04 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-08 16:39 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-07 23:44 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-06 15:14 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-05 17:40 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-03 14:22 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-02 16:22 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-10-01 19:46 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-30 15:35 UTCEG score recompute
- 2026-09-30 15:00 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-29 15:15 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-28 13:47 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-27 13:41 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-26 15:54 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-26 00:21 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-24 14:00 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-23 13:44 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-21 20:28 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-19 15:37 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-18 19:23 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-17 19:23 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-16 14:05 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-15 03:06 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-12 14:57 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-11 14:49 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-11 09:33 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-08 21:56 UTCEPSS rescoreEPSS 3.5% · 88th percentile
- 2026-09-07 15:58 UTCEPSS rescoreEPSS 3.5% · 88th percentile
Publicly available exploits
(1 reference)Public exploit code is referenced for this CVE (1 GitHub PoC). No fix has been recorded since the CVE record was published in 2021. If the vendor still supports the product, apply the fixed version it names; if it no longer does, isolate the affected system or retire the product.
- GitHub PoCfloesen/CVE-2021-30481Published 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?
When was the CVE record for CVE-2021-30481 published?
Is CVE-2021-30481 actively exploited?
What is the CVSS score of CVE-2021-30481?
How do I remediate CVE-2021-30481?
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2021-30481
Is Your Infrastructure Affected by CVE-2021-30481?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.