MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure

Summary MessagePack::Bufferclear shifts out every chunk and returns its 4 KiB rmem page to the shared pool, but does not reset the buffer's rmem cursor rmemlast, rmemend, rmemowner. The next write sees "unused rmem space" left over from the freed page and hands back a slice of memory that has...

CVE-2026-54522 MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure

MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Bufferclear in ext/msgpack/buffer.c leaves rmemlast, rmemend, and rmemowner stale after msgpackbuffershiftchunk returns an rmem page to the shared pool, allowing a subsequent...

CVE-2026-54522

CVE-2026-54522 affects MessagePack for Ruby prior to 1.8.2. The vulnerability lies in MessagePack::Buffer#clear in ext/msgpack/buffer.c, which leaves rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool. A subsequent Buffer#write by a...

CVE-2026-54522 MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure

MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Bufferclear in ext/msgpack/buffer.c leaves rmemlast, rmemend, and rmemowner stale after msgpackbuffershiftchunk returns an rmem page to the shared pool, allowing a subsequent...

CVE-2026-54522

MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Bufferclear in ext/msgpack/buffer.c leaves rmemlast, rmemend, and rmemowner stale after msgpackbuffershiftchunk returns an rmem page to the shared pool, allowing a subsequent...