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gh-160314: Raise for a damaged later stream in lzma and bz2 - #160315
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A damaged .xz or bzip2 stream that followed another stream was taken for trailing data and silently ignored. Leftover data that starts with the stream magic is now treated as a stream, as gzip does.
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gpshead
added
needs backport to 3.14
gpshead
commented
Oct 31, 2026
gpshead
marked this pull request as ready for review
October 31, 2026 19:39
gpshead
enabled auto-merge (squash)
October 31, 2026 19:40
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Thanks @gpshead for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14, 3.15. |
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Sorry, @gpshead, I could not cleanly backport this to Please backport manually with cherry_picker, see the devguide for more information. |
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Sorry, @gpshead, I could not cleanly backport this to Please backport manually with cherry_picker, see the devguide for more information. |
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GH-161034 is a backport of this pull request to the 3.15 branch. |
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GH-161035 is a backport of this pull request to the 3.14 branch. |
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Oct 31, 2026
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DecompressReader.read(),lzma.decompress()andbz2.decompress()now ignore leftover data after a stream only when it does not start with the format's stream magic (the six.xzheader bytes, orBZh1toBZh9as thebzip2program requires); an error in data that does start with it is propagated. This is the same heuristicgzipuses to tell another member from trailing data. Trailing junk that happens to start with the magic bytes now raises instead of being ignored. A damaged later stream in the legacy.lzmacontainer, which has no magic, is still dropped silently.This touches the same
decompress()loops inLib/bz2.pyandLib/lzma.pyas GH-160311, so the two conflict textually; whichever is merged second needs a rebase.Fixes #160314
ANT-2026-3TVAVL5A
lzmaandbz2silently ignore a damaged later stream as trailing data #160314