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GeezerVison is showing github.com — gh-159739: Handle pyexpat configuration changes during callbacks by jelle-openai · Pull Request #160399 · python/cpython

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@jelle-openai

@jelle-openai jelle-openai commented Oct 22, 2026 •
edited by bedevere-app Bot
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A character data callback can disable buffering or remove the next event handler during a flush. Interning an attribute name can also change ordered_attributes while pyexpat is filling the attribute container. Using the freed buffer, cleared handler, or wrong container type can crash the interpreter. Clear the buffered length before dispatch, keep the active handler alive, recheck the buffer and handlers after callbacks, and use one attribute mode for the whole start event.

  • Issue: Fix minor safety issues #159739

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@jelle-openai
pythongh-159739: Handle pyexpat configuration changes during callbacks
55c3a8a
A character data callback can disable buffering or remove the next event handler during a flush. Interning an attribute name can also change ordered_attributes while pyexpat is filling the attribute container. Using the freed buffer, cleared handler, or wrong container type can crash the interpreter. Clear the buffered length before dispatch, keep the active handler alive, recheck the buffer and handlers after callbacks, and use one attribute mode for the whole start event.
@bedevere-app bedevere-app Bot added the awaiting review label Oct 22, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Oct 22, 2026
Fix minor safety issues #159739
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@JelleZijlstra
JelleZijlstra merged commit 0ba58e7 into python:main Oct 23, 2026
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@bedevere-app bedevere-app Bot removed the awaiting review label Oct 23, 2026
@JelleZijlstra JelleZijlstra added awaiting review needs backport to 3.14 bugs and security fixes needs backport to 3.15 bugs and security fixes labels Oct 23, 2026
@miss-islington-app

miss-islington-app Bot commented Oct 23, 2026

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

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@miss-islington-app

miss-islington-app Bot commented Oct 23, 2026

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Thanks @jelle-openai for the PR, and @JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

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@bedevere-app

bedevere-app Bot commented Oct 23, 2026

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GH-160474 is a backport of this pull request to the 3.14 branch.

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@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Oct 23, 2026
@bedevere-app

bedevere-app Bot commented Oct 23, 2026

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GH-160475 is a backport of this pull request to the 3.15 branch.

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@bedevere-app bedevere-app Bot removed the needs backport to 3.15 bugs and security fixes label Oct 23, 2026
JelleZijlstra pushed a commit that referenced this pull request Oct 24, 2026
@miss-islington @jelle-openai
[3.14] gh-159739: Handle pyexpat configuration changes during callbac…
282a34e
…ks (GH-160399) (#160474)

A character data callback can disable buffering or remove the next event handler during a flush. Interning an attribute name can also change ordered_attributes while pyexpat is filling the attribute container. Using the freed buffer, cleared handler, or wrong container type can crash the interpreter. Clear the buffered length before dispatch, keep the active handler alive, recheck the buffer and handlers after callbacks, and use one attribute mode for the whole start event.
(cherry picked from commit 0ba58e7)

Co-authored-by: Jelle Zijlstra <[email protected]>
JelleZijlstra pushed a commit that referenced this pull request Oct 24, 2026
@miss-islington @jelle-openai
[3.15] gh-159739: Handle pyexpat configuration changes during callbac…
0ab39af
…ks (GH-160399) (#160475)

A character data callback can disable buffering or remove the next event handler during a flush. Interning an attribute name can also change ordered_attributes while pyexpat is filling the attribute container. Using the freed buffer, cleared handler, or wrong container type can crash the interpreter. Clear the buffered length before dispatch, keep the active handler alive, recheck the buffer and handlers after callbacks, and use one attribute mode for the whole start event.
(cherry picked from commit 0ba58e7)

Co-authored-by: Jelle Zijlstra <[email protected]>
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@jelle-openai @JelleZijlstra
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