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[3.11] gh-90949: expose Expat API to tune exponential expansion protections (GH-139368) (GH-151401) - #155346

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pablogsal merged 2 commits into
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StanFromIreland:backport-db195e3-3.11
Aug 9, 2026
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[3.11] gh-90949: expose Expat API to tune exponential expansion protections (GH-139368) (GH-151401)#155346
pablogsal merged 2 commits into
python:3.11from
StanFromIreland:backport-db195e3-3.11

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@StanFromIreland

@StanFromIreland StanFromIreland commented Aug 7, 2026

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Expose the XML Expat 2.7.2 APIs to tune protections against "billion laughs" [1] attacks.

The exposed APIs are available on Expat parsers, that is, parsers created by xml.parsers.expat.ParserCreate(), as:

  • parser.SetBillionLaughsAttackProtectionActivationThreshold(threshold), and
  • parser.SetBillionLaughsAttackProtectionMaximumAmplification(max_factor).

This completes the work in f04bea4, and improves the existing related documentation.

[1]: https://en.wikipedia.org/wiki/Billion_laughs_attack (cherry picked from commit 6661123) (cherry picked from commit 19bc391) (cherry picked from commit db195e3)

… protections (pythonGH-139368) (pythonGH-151401)

Expose the XML Expat 2.7.2 APIs to tune protections against
"billion laughs" [1] attacks.

The exposed APIs are available on Expat parsers, that is,
parsers created by `xml.parsers.expat.ParserCreate()`, as:

- `parser.SetBillionLaughsAttackProtectionActivationThreshold(threshold)`, and
- `parser.SetBillionLaughsAttackProtectionMaximumAmplification(max_factor)`.

This completes the work in f04bea4,
and improves the existing related documentation.

[1]: https://en.wikipedia.org/wiki/Billion_laughs_attack
(cherry picked from commit 6661123)
(cherry picked from commit 19bc391)
(cherry picked from commit db195e3)

Co-authored-by: Stan Ulbrych <stan@python.org>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
@StanFromIreland

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The only conflict was in the generated AC.

@pablogsal
pablogsal merged commit 3c1801a into python:3.11 Aug 9, 2026
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@StanFromIreland
StanFromIreland deleted the backport-db195e3-3.11 branch August 9, 2026 18:19
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2 participants