Teeworlds is an online multi-player platform 2D shooter.
Teeworlds client contains a vulnerability allowing a malicious server to execute arbitrary code, or write to arbitrary physical memory via the CClient::ProcessServerPacket method.
A remote malicious server can write to arbitrary physical memory locations and possibly execute arbitrary if a vulnerable client joins the server.
There is no known workaround at this time.
All Teeworlds users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=games-action/teeworlds-0.6.4:0"