CVE-2017-20205 Valve Source SDK Stack-Based Buffer Overflow RCE
Remote attackers can execute arbitrary code on clients or servers by sending a crafted ragdoll model that triggers a stack-based buffer overflow in the Source SDK.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2017-20205?
CVE-2017-20205 is a critical memory corruption vulnerability in Valve Software Source SDK (source-sdk-2013), published on 15 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-121
Which versions are affected by CVE-2017-20205?
How do I fix CVE-2017-20205?
No fix has been published for CVE-2017-20205 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2017-20205 being exploited?
There is no known exploitation of CVE-2017-20205 in the wild and no public exploit code.
Sources
Also known as GHSA-g2mq-5mgx-wg6w.