Valve's Source SDK (source-sdk-2013)'s ragdoll model parsing logic contains a stack-based buffer overflow vulnerability.The tokenizer function nexttoken copies characters from an input string into a fixed-size stack buffer without performing bounds checks. When ParseKeyValue processes a collisionpair rule longer than the destination buffer (256 bytes), an overflow of the stack buffer szToken can occur and overwrite the function return address. A remote attacker can trigger the vulnerable code by supplying a specially crafted ragdoll model which causes the oversized collisionpair rule to be parsed, resulting in remote code execution on affected clients or servers. Valve has addressed this issue in many of their Source games, but independently-developed games must manually apply patch.
CVE-2017-20205
This critical-severity CVE scores 9.2 under NVD CVSS v3. EPSS exploit probability: 0.6%, top 53% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 9.2
- EG Score
- 9.2(medium)
- EG Risk
- 57(Track)EG Risk 57/100SSVC: 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 computedSeverity92% × 45%Exploitation1% × 40%Automatability100% × 15%Action: Routine — remediate on your standard cadence. - EPSS
- 47.2%
- KEV
- Not listed
Published
October 15, 2025
Last Modified
April 15, 2026
Advisory Details (3)
Auto-updated Jul 18, 2026Valve Source SDK Stack-Based Buffer Overflow RCE | Advisories | VulnCheck
https://www.vulncheck.com/advisories/valve-source-sdk-stack-based-buffer-overflow-rceRemote Code Execution In Source Games – One Up Security, LLC
https://www.oneupsecurity.com/research/remote-code-execution-in-source-games/GitHub - ValveSoftware/source-sdk-2013: The 2013 edition of the Source SDK · GitHub
https://github.com/ValveSoftware/source-sdk-2013Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 14× in last 7d / 42× 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.
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Related CVEs(same CWE)
Same CWE
10 shownCWE-121
Frequently asked(5)
What is CVE-2017-20205?
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What is the CVSS score of CVE-2017-20205?
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Dependency Blast Radius
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