1. Values flagged as compressed were inflated with no size limit. A ~130 KB stored item expands to 128 MB on read (about 1000:1), regardless of the client's compress or serializer settings.
2. The size in a reply (a meta VA <size>, or a binary body length) was used to read or buffer that many bytes, so a hostile or compromised server could make the client allocate gigabytes.

Exploiting either requires write access to the memcached instance (a shared or exposed instance, another tenant), or a malicious server or proxy. Patched versions add a decompressed_max_bytes option (default 128 MiB) and reject reply sizes over 1 GiB.