CVE-2017-20205

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.

PUBLISHED Reserved 2025-10-14 | Published 2025-10-15 | Updated 2025-10-15 | Assigner VulnCheck

Problem types

CWE-121 Stack-based Buffer Overflow

Product status

Credits

One Up Security, LLC finder

References

www.oneupsecurity.com/...ote-code-execution-in-source-games/ technical-description patch

github.com/ValveSoftware/source-sdk-2013 product

www.vulncheck.com/...rce-sdk-stack-based-buffer-overflow-rce third-party-advisory

cve.org (CVE-2017-20205)

nvd.nist.gov (CVE-2017-20205)

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