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                            CERT-Renater

                Note d'Information No. 2025/VULN477
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DATE                : 30/07/2025

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S): Systems running CPython.

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https://mail.python.org/archives/list/security-announce@python.org/thread/ZULLF3IZ726XP5EY7XJ7YIN3K5MDYR2D/
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[CVE-2025-8194] Tarfile infinite loop during parsing with negative
member offset

Seth Larson
28 juillet 2025 18:44

There is a HIGH severity vulnerability affecting {project}.

There is a defect in the CPython “tarfile” module affecting the
“TarFile” extraction and entry enumeration APIs. The tar implementation
would process tar archives with negative offsets without error,
resulting in an infinite loop and deadlock during the parsing of
maliciously crafted tar archives.

This vulnerability can be mitigated by including the following patch
after importing the “tarfile” module:

import tarfile

def _block_patched(self, count):
if count < 0: # pragma: no cover
raise tarfile.InvalidHeaderError("invalid offset")
return _block_patched._orig_block(self, count)

_block_patched._orig_block = tarfile.TarInfo._block
tarfile.TarInfo._block = _block_patched

Please see the linked CVE ID for the latest information on
affected versions:

    https://www.cve.org/CVERecord?id=CVE-2025-8194
    https://github.com/python/cpython/pull/137027


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