TI-2017-14271 Aliases CVE-2017-20205 GHSA-g2mq-5mgx-wg6w

Valve Source SDK Stack-Based Buffer Overflow RCE

MEDIUM 49CWE-121Published 2025-10-15 · Updated 2025-11-21

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: Present
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-121 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00693 53rd percentileScored 2026-11-07

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Valve Software	Source SDK (source-sdk-2013)	source-sdk-2013	—	No fix listed	CNA

Source SDK (source-sdk-2013) VendorValve Software Affected source-sdk-2013 Fixed in — No fix listed CNA

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2017-20205
2026-10-03 Alias added: GHSA-g2mq-5mgx-wg6w

References

Patch 1

https://www.oneupsecurity.com/research/remote-code-execution-in-source-games/

Other 1

https://github.com/ValveSoftware/source-sdk-2013

TI-2000-00959 Format string vulnerability in Half Life dedicated server build 3104 and earlier allows… CVSS 2.0HIGH 10.0
TI-2000-00958 Buffer overflow in Half Life dedicated server before build 3104 allows remote attackers… CVSS 2.0HIGH 10.0
TI-2001-00353 Buffer overflows in Sierra Half-Life build 1573 and earlier allow remote attackers to… CVSS 2.0HIGH 7.5
TI-2007-05486 Off-by-one error in the GeoIP module in the AMX Mod X 1.76d plugin for Half-Life Server… CVSS 2.0HIGH 7.5
TI-2001-00920 Buffer overflow in client for Half-Life 1.1.0.8 and earlier allows malicious remote… CVSS 2.0HIGH 7.5
TI-2001-00354 Format string vulnerability in Sierra Half-Life build 1573 and earlier allows a remote… CVSS 2.0HIGH 7.5

See all 11 →

Sources

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