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The zlib Decompress.decompress has a max_length parameter that limits the size of the returned uncompressed data.
The lzma and bz2 decompress methods do not have such a parameter.
Therefore, it is not possible to decompress untrusted lzma or bz2 data without becoming susceptible to a DoS attack, as the attacker can force allocation of gigantic buffers by sending just a tiny amount of compressed data:
$ dd if=/dev/zero bs=128k count=10k | bzip2 -9 > nasty.bz2
10240+0 records in
10240+0 records out
1342177280 bytes (1.3 GB) copied, 11.0892 s, 121 MB/s
$ dir nasty.bz2 
-rw-rw-r-- 1 nikratio nikratio 977 Apr 21 14:58 nasty.bz2
It would be great if the lzma and bz2 decompressor methods could also get a max_length parameters to make this situation less threatening.