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gh-103051: validate EOCD archive-comment-length in zipimport - #161929
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BHUVANSH855 wants to merge 2 commits into
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BHUVANSH855
requested review from
FFY00,
brettcannon,
ericsnowcurrently,
ncoghlan and
warsaw
as code owners
November 13, 2026 08:11
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zipimport._read_directory() located the EOCD record using rfind(b'PK\x05\x06')
but never validated that the archive-comment-length field (bytes 20-21) was
consistent with the actual file size. A crafted .pyc whose bytecode contains
the EOCD signature could be misidentified as a ZIP archive (pyc/zip polyglot).
Add the invariant check:
header_position + END_CENTRAL_DIR_SIZE + comment_size == file_size
This holds for all valid ZIPs (plain, with archive comment, with prepended
bytes such as PEX or self-extracting .exe). Files where the signature is
spurious fail the check and raise ZipImportError.
Closes issue #103051