GHSA-wc9c-hfh3-phxx: SimulationCraft: Heap-Based Buffer Overflow / Out-of-Bounds Write in SimulationCraft's gem_id Array

SimulationCraft is a tool to explore combat mechanics in World of Warcraft. In builds after release-820-01 and before the identified May 7, 2026 nightly, the bcpapi.cpp loop over the JSON sockets array uses slotdata["sockets"].Size() without bounding gemidx by MAXGEMSLOTS, which is four in engine/scenums.hpp. The destination gemid and gembonusid arrays in engine/item/item.hpp have only four elements. More than four socket entries therefore write beyond gemid into the adjacent gembonusid vector storage; bonuslist entries can also access gembonusid out of bounds. Corrupting a vector's Mstart pointer causes the itemt destructor to free an attacker-influenced pointer during normal cleanup. The advisory reports crashes and code execution demonstrated in a testing environment. Attack inputs can arrive through a malicious .simc profile with a [[equipment]] section, a compromised addon export, or Battle.net API responses modified by an attacker with a privileged network position. The fix is contained in the nightly build identified as simc-1205-01-516b5d7; no containing release tag is available.