Expose Expat XML attack protection APIs

[gpshead]

BPO	46793
Nosy	@gpshead, @hartwork, @corona10

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2022-02-18.21:27:31.809>
labels = ['type-feature', '3.11']
title = 'expose expat XML billion laughs attack mitigation APIs'
updated_at = <Date 2022-02-25.02:16:52.654>
user = 'https://github.com/gpshead'

bugs.python.org fields:

activity = <Date 2022-02-25.02:16:52.654>
actor = 'sping'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2022-02-18.21:27:31.809>
creator = 'gregory.p.smith'
dependencies = []
files = []
hgrepos = []
issue_num = 46793
keywords = []
message_count = 2.0
messages = ['413513', '413955']
nosy_count = 3.0
nosy_names = ['gregory.p.smith', 'sping', 'corona10']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue46793'
versions = ['Python 3.11']

Linked PRs

• gh-90949: add Expat API to prevent XML deadly allocations #139234
• gh-90949: amend GH-139234 in prevision of future mitigation API #139366
• [3.14] gh-90949: add Expat API to prevent XML deadly allocations (CVE-2025-59375) (GH-139234) #139359
• [3.13] gh-90949: add Expat API to prevent XML deadly allocations (CVE-2025-59375) (GH-139234) #139367
• [3.12] gh-90949: add Expat API to prevent XML deadly allocations (CVE-2025-59375) (GH-139234) #139527
• [3.11] gh-90949: add Expat API to prevent XML deadly allocations (CVE-2025-59375) (GH-139234) #139529
• [3.10] gh-90949: add Expat API to prevent XML deadly allocations (CVE-2025-59375) (GH-139234) #139532
• gh-90949: expose Expat API to tune exponential expansion protections #139368
• gh-90949: Fix an "unused function" compiler warning introduced in GH-139234 #139558
• gh-90949: Recommend hasattr with Expat security methods #139800
• [3.14] gh-90949: expose Expat API to tune exponential expansion protections (GH-139368) #150496
• gh-90949: Fix copy-paste typo in pyexpat capsule API initialization #151147
• [3.13] gh-90949: expose Expat API to tune exponential expansion protections (GH-139368) #151151
• [3.12] gh-90949: expose Expat API to tune exponential expansion protections (GH-139368) #151401
• [3.15] gh-90949: Fix copy-paste typo in pyexpat capsule API initialization (GH-151147) #152088
• [3.11] gh-90949: expose Expat API to tune exponential expansion protections (GH-139368) (GH-151401) #155346
• [3.10] gh-90949: expose Expat API to tune exponential expansion protections (GH-139368) (#151401) #155414

[gpshead]

Quoting from #31397 (comment)

"""
XML_SetBillionLaughsAttackProtectionActivationThreshold

XML_SetBillionLaughsAttackProtectionMaximumAmplification

I still hope that someone can make those two^^ accessible (with additional glue code) to the user on pyexpat level in CPython.
""" - Sebastian Pipping @hartwork

[hartwork]

First mention at https://bugs.python.org/issue44394#msg395642

[hartwork]

FYI starting with Expat 2.7.2, there are two new API functions more related to both security and amplification:

• XML_SetAllocTrackerActivationThreshold
• XML_SetAllocTrackerMaximumAmplification