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gh-148093: Raise binascii.Error from binascii.a2b_uu on empty input#149077

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serhiy-storchaka merged 6 commits intopython:mainfrom
maurycy:a2buu-err
May 4, 2026
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gh-148093: Raise binascii.Error from binascii.a2b_uu on empty input#149077
serhiy-storchaka merged 6 commits intopython:mainfrom
maurycy:a2buu-err

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@maurycy maurycy commented Apr 27, 2026 •
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Right now, binascii.a2b_uu with empty data reads one byte past the end of the input buffer. Per the discussion, it should raise binascii.Error.

Resolves #148093

@bedevere-app bedevere-app Bot mentioned this pull request Apr 27, 2026
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maurycy commented Apr 27, 2026

cc @serhiy-storchaka

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Comment thread Lib/test/test_binascii.py
self.assertRaises(binascii.Error, binascii.a2b_uu, b"!!!!")
self.assertRaises(binascii.Error, binascii.a2b_uu,
self.type2test(b""))
self.assertRaises(binascii.Error, binascii.a2b_uu,
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Do we need this second test case? The [:0] makes it an empty sequence?

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@maurycy maurycy Apr 27, 2026 •
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@sethmlarson

cpython/Lib/test/test_binascii.py

Lines 1622 to 1623 in 005555a

class MemoryviewBinASCIITest(BinASCIITest):
type2test = memoryview

memoryview(b"#86)C")[:0] is the actual UB case here: zero slice with larger underlying buffer

@serhiy-storchaka came up with it:

#148093 (comment)

Truth to be told, this BinASCIITest inheritance is very confusing and make lots of tests without self.type2test redundant but I didn't want to overhaul it. Do you want me to create a separate issue documenting problems with BinASCIITest?

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BTW, #86)C is a uuencoded b'abc', the simplest non-trivial example. It has no any relation to the current, the past or the future US presidents.

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LGTM. 👍

Comment thread Lib/test/test_binascii.py
self.assertRaises(binascii.Error, binascii.a2b_uu, b"!!!!")
self.assertRaises(binascii.Error, binascii.a2b_uu,
self.type2test(b""))
self.assertRaises(binascii.Error, binascii.a2b_uu,
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BTW, #86)C is a uuencoded b'abc', the simplest non-trivial example. It has no any relation to the current, the past or the future US presidents.

@serhiy-storchaka serhiy-storchaka merged commit 0c6d2f6 into python:main May 4, 2026
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@serhiy-storchaka serhiy-storchaka added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels May 4, 2026
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miss-islington-app Bot commented May 4, 2026

Thanks @maurycy for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

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miss-islington-app Bot commented May 4, 2026

Thanks @maurycy for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

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bedevere-app Bot commented May 4, 2026

GH-149349 is a backport of this pull request to the 3.13 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.13 bugs and security fixes label May 4, 2026
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bedevere-app Bot commented May 4, 2026

GH-149350 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label May 4, 2026
serhiy-storchaka pushed a commit that referenced this pull request May 4, 2026
@miss-islington @maurycy
[3.13] gh-148093: Raise binascii.Error from binascii.a2b_uu() on empt…
023ecbd 
…y input (GH-149077) (GH-149349)

Instead of reading past the end of the empty buffer.
(cherry picked from commit 0c6d2f6)

Co-authored-by: Maurycy Pawłowski-Wieroński <maurycy@maurycy.com>
serhiy-storchaka pushed a commit that referenced this pull request May 4, 2026
@miss-islington @maurycy
[3.14] gh-148093: Raise binascii.Error from binascii.a2b_uu() on empt…
3e25cd9 
…y input (GH-149077) (GH-149350)

Instead of reading past the end of the empty buffer.
(cherry picked from commit 0c6d2f6)

Co-authored-by: Maurycy Pawłowski-Wieroński <maurycy@maurycy.com>
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binascii.a2b_uu() reads past the end of empty buffer

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