CVE-2026-47683: vm2's bufferAllocLimit cap bypassed by Buffer.concat and Buffer.from arrayLike

vm2 bufferAllocLimit cap bypassed by Buffer.concat and Buffer.from arrayLike

The bufferAllocLimit option introduced in 3.11.0 (GHSA-6785-pvv7-mvg7) caps host-side Buffer allocations driven by sandbox code, the way embedders opt into timeout. The cap wraps Buffer.alloc, Buffer.allocUnsafe, Buffer.allocUnsafeSlow, and the deprecated Buffer(N) / new Buffer(N) forms. Two other API paths reach the same host C++ allocator with an attacker-controlled size and are not capped: Buffer.concat(list, totalLength) and Buffer.from(arrayLike) with a fake length. Sandbox code can use either to allocate an arbitrary number of host external bytes in a single call, defeating the explicit DoS mitigation the embedder configured.