CVE-2017-20205

Valve Source SDK Stack-Based Buffer Overflow RCE

Published Oct 15, 2025 CVSS 4.0 · 9.2 Critical EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Valvesoftware source
CPEs cpe:2.3:a:valvesoftware:source:source-sdk-2013:*:*:*:*:*:*:*
Vendors & Products Valvesoftware source
Type Values Removed Values Added
First Time appeared Valvesoftware
Valvesoftware source Sdk
Vendors & Products Valvesoftware
Valvesoftware source Sdk
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title Valve Source SDK Stack-Based Buffer Overflow RCE
Weaknesses CWE-121
References
Metrics cvssV4_0

{'score': 9.2, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Nov 21, 2025, 2:19 PM
Reserved
Oct 14, 2025, 6:50 PM
Status
Deferred
Published
Oct 15, 2025, 2:15 AM
Modified
Jun 17, 2026, 1:15 AM