gh-149486: tarfile.data_filter: validate written link target#149487
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encukou merged 3 commits intoMay 8, 2026
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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.
encukou
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needs backport to 3.12
gpshead
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May 7, 2026
StanFromIreland
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needs backport to 3.15
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Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12, 3.13, 3.14, 3.15. |
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GH-149553 is a backport of this pull request to the 3.15 branch. |
bedevere-app
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needs backport to 3.15
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GH-149554 is a backport of this pull request to the 3.14 branch. |
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GH-149555 is a backport of this pull request to the 3.13 branch. |
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GH-149556 is a backport of this pull request to the 3.12 branch. |
encukou
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May 11, 2026
…H-149487) (GH-149553) gh-149486: tarfile.data_filter: validate written link target (GH-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. (cherry picked from commit 5784119) Co-authored-by: Gregory P. Smith <greg@krypto.org>
encukou
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May 11, 2026
…H-149487) (GH-149554) * gh-149486: tarfile.data_filter: validate written link target (GH-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 <encukou@gmail.com> Co-authored-by: Gregory P. Smith <greg@krypto.org>
encukou
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May 11, 2026
…H-149487) (GH-149555) * gh-149486: tarfile.data_filter: validate written link target (GH-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 <encukou@gmail.com> Co-authored-by: Gregory P. Smith <greg@krypto.org>
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