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GeezerVison is showing github.com — [3.10] gh-149486: tarfile.data_filter: validate written link target (GH-149487) by StanFromIreland · Pull Request #153180 · python/cpython

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@StanFromIreland

@StanFromIreland StanFromIreland commented Jul 6, 2026 •
edited by bedevere-app Bot
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The data filter rewrote linknames with normpath() but ran the containment check against the un-normalised value, and computed a symlink's directory before stripping trailing slashes. Both let a crafted archive create links pointing outside the destination. Also reject link members that resolve to the destination directory itself, which could otherwise replace it with a symlink and redirect all subsequent members.

(Patch by Greg; Petr's just reviewing & merging.)
(cherry picked from commit 5784119)

  • Issue: tarfile.data_filter doesn't handle symlinks with empty names #149486

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@encukou @gpshead @StanFromIreland
[3.10] pythongh-149486: tarfile.data_filter: validate written link ta…
6fd7650 
…rget (pythonGH-149487)

The data filter rewrote linknames with normpath() but ran the
containment check against the un-normalised value, and computed a
symlink's directory before stripping trailing slashes.  Both let a
crafted archive create links pointing outside the destination.  Also
reject link members that resolve to the destination directory itself,
which could otherwise replace it with a symlink and redirect all
subsequent members.

(Patch by Greg; Petr's just reviewing & merging.)
(cherry picked from commit 5784119)

Co-authored-by: Petr Viktorin <[email protected]>
Co-authored-by: Gregory P. Smith <[email protected]>
@StanFromIreland
StanFromIreland requested a review from ethanfurman as a code owner July 6, 2026 09:21
This was referenced Jul 6, 2026
tarfile.data_filter doesn't handle symlinks with empty names #149486
Closed
gh-149486: tarfile.data_filter: validate written link target #149487
Merged
@bedevere-app bedevere-app Bot added the awaiting core review label Jul 6, 2026
@StanFromIreland

StanFromIreland commented Jul 6, 2026

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Based on #150904.
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@StanFromIreland StanFromIreland assigned StanFromIreland and pablogsal and unassigned StanFromIreland Jul 6, 2026
@pablogsal
pablogsal merged commit c063191 into python:3.10 Jul 6, 2026
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@bedevere-app bedevere-app Bot removed the awaiting core review label Jul 6, 2026
@StanFromIreland
StanFromIreland deleted the backport-5784119-3.10 branch July 6, 2026 19:56
icanhasmath pushed a commit to ActiveState/cpython that referenced this pull request Oct 28, 2026
@StanFromIreland @icanhasmath
[3.10] pythongh-149486: tarfile.data_filter: validate written link ta…
b6f6db1 
…rget (pythonGH-149487) (python#153180)

(cherry picked from commit c063191)
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@ethanfurman ethanfurman Awaiting requested review from ethanfurman ethanfurman is a code owner

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@pablogsal pablogsal

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3 participants

@StanFromIreland @pablogsal @encukou
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