Msgpack Ruby
Monthly
Cross-buffer memory aliasing in msgpack-ruby prior to 1.8.2 allows same-process code to read or corrupt data belonging to a separate MessagePack::Buffer instance via a use-after-free in the rmem slab allocator. MessagePack::Buffer#clear returns a 4 KiB rmem page to the shared pool but leaves rmem_last, rmem_end, and rmem_owner pointing into the freed page; a subsequent write on the cleared buffer and a concurrent second Buffer allocation can claim the same physical page, creating a memory alias that exposes the second buffer's serialized bytes. A PoC is included in the vendor advisory (GHSA-4mrv-5p47-p938); no public exploit identified at time of analysis beyond that PoC, and the CVE is not in CISA KEV.
Cross-buffer memory aliasing in msgpack-ruby prior to 1.8.2 allows same-process code to read or corrupt data belonging to a separate MessagePack::Buffer instance via a use-after-free in the rmem slab allocator. MessagePack::Buffer#clear returns a 4 KiB rmem page to the shared pool but leaves rmem_last, rmem_end, and rmem_owner pointing into the freed page; a subsequent write on the cleared buffer and a concurrent second Buffer allocation can claim the same physical page, creating a memory alias that exposes the second buffer's serialized bytes. A PoC is included in the vendor advisory (GHSA-4mrv-5p47-p938); no public exploit identified at time of analysis beyond that PoC, and the CVE is not in CISA KEV.