The xmlrpc client library is the only stdlib module that has a gzip decompression handler for compressed HTTP streams. The gzip_decode() function decompresses HTTP bodies that are compressed and sent with Accept-Encoding: x-gzip.

A malicious server can send a specially prepared HTTP request that can consume lots of memory. For example 1 GB of \0 bytes is less than 1 MB of gzip data.

Suggestion:
The gzip_decode() should only decode a sane amount of bytes (for example 50 MB) and raise an exception when more data is to be read.