CVE-2020-6016

Valves 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.

Weakness

The product calls free() on a pointer to memory that was not allocated using associated heap allocation functions such as malloc(), calloc(), or realloc().

Affected Software

Potential Mitigations

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, glibc in Linux provides protection against free of invalid pointers.

References

• https://github.com/ValveSoftware/GameNetworkingSockets/commit/e0c86dcb9139771db3db0cfdb1fb8bef0af19c43
• https://research.checkpoint.com/2020/game-on-finding-vulnerabilities-in-valves-steam-sockets/
• https://github.com/ValveSoftware/GameNetworkingSockets/commit/e0c86dcb9139771db3db0cfdb1fb8bef0af19c43
• https://research.checkpoint.com/2020/game-on-finding-vulnerabilities-in-valves-steam-sockets/