A directory traversal vulnerability in Valve Counter-Strike 8684 allows a client (with remote control access to a game server) to read arbitrary files from the underlying server via the motdfile console variable.

A buffer overflow in Counter-Strike through 8684 allows a game server to execute arbitrary code on a remote client's machine by modifying the lservercfgfile console variable.

A buffer overflow in the component hl.exe of Valve Half-Life up to 5433873 allows attackers to execute arbitrary code and escalate privileges by supplying crafted parameters.

Valve Steam through 2021-04-10, when a Source engine game is installed, allows remote authenticated users to execute arbitrary code because of a buffer overflow that occurs for a Steam invite after one click.

Valve's Game Networking Sockets prior to version v1.2.0 improperly handles long unreliable segments in function SNP_ReceiveUnreliableSegment() when configured to support plain-text messages, leading to a Heap-Based Buffer Overflow and resulting in a memory corruption and possibly even a remote code execution.

Valve's Game Networking Sockets prior to version v1.2.0 improperly handles long encrypted messages in function AES_GCM_DecryptContext::Decrypt() when compiled using libsodium, leading to a Stack-Based Buffer Overflow and resulting in a memory corruption and possibly even a remote code execution.

Valve's Game Networking Sockets prior to version v1.2.0 improperly handles unreliable segments with negative offsets in function SNP_ReceiveUnreliableSegment(), leading to a Heap-Based Buffer Underflow and a free() of memory not from the heap, resulting in a memory corruption and probably even a remote code execution.

Valve's Game Networking Sockets prior to version v1.2.0 improperly handles inlined statistics messages in function CConnectionTransportUDPBase::Received_Data(), leading to an exception thrown from libprotobuf and resulting in a crash.

An issue was discovered in Valve Steam Client 2.10.91.91. The installer allows local users to gain NT AUTHORITY\SYSTEM privileges because some parts of %PROGRAMFILES(X86)%\Steam and/or %COMMONPROGRAMFILES(X86)%\Steam have weak permissions during a critical time window. An attacker can make this time window arbitrarily long by using opportunistic locks.

Valve Source allows local users to gain privileges by writing to the /tmp/hl2_relaunch file, which is later executed in the context of a different user account.