[issue42103] [security] DoS (MemError via CPU and RAM exhaustion) when processing malformed Apple Property List files in binary format

[Serhiy Storchaka]

Serhiy Storchaka <storchaka+cpython at gmail.com> added the comment:

There are two issues here.

The simple one is building a large format string for struct.unpack(). It has simple solution: use f'>{n}{_BINARY_FORMAT[size]}'.

The hard issue is that read(n) allocates n bytes in memory even if there are not so many bytes in the file. It affects not only plistlib and should be fixed in the file implementation itself. There is an open issue for this.

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<https://bugs.python.org/issue42103>
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