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[3.10] gh-115399: Document CVE-2023-52425 under "XML vulnerabilities" (GH-115400) #115762

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Feb 21, 2024
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[3.10] gh-115399: Document CVE-2023-52425 under "XML vulnerabilities" (GH-115400) #115762

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13 changes: 13 additions & 0 deletions Doc/library/xml.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,7 @@ quadratic blowup **Vulnerable** (1) **Vulnerable** (1) **Vulnerable*
external entity expansion Safe (5) Safe (2) Safe (3) Safe (5) Safe (4)
`DTD`_ retrieval Safe (5) Safe Safe Safe (5) Safe
decompression bomb Safe Safe Safe Safe **Vulnerable**
large tokens **Vulnerable** (6) **Vulnerable** (6) **Vulnerable** (6) **Vulnerable** (6) **Vulnerable** (6)
========================= ================== ================== ================== ================== ==================

1. Expat 2.4.1 and newer is not vulnerable to the "billion laughs" and
Expand All @@ -81,6 +82,11 @@ decompression bomb Safe Safe Safe
4. :mod:`xmlrpclib` doesn't expand external entities and omits them.
5. Since Python 3.7.1, external general entities are no longer processed by
default.
6. Expat 2.6.0 and newer is not vulnerable to denial of service
through quadratic runtime caused by parsing large tokens.
Items still listed as vulnerable due to
potential reliance on system-provided libraries. Check
:const:`!pyexpat.EXPAT_VERSION`.


billion laughs / exponential entity expansion
Expand Down Expand Up @@ -114,6 +120,13 @@ decompression bomb
files. For an attacker it can reduce the amount of transmitted data by three
magnitudes or more.

large tokens
Expat needs to re-parse unfinished tokens; without the protection
introduced in Expat 2.6.0, this can lead to quadratic runtime that can
be used to cause denial of service in the application parsing XML.
The issue is known as
`CVE-2023-52425 <https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-52425>`_.

The documentation for `defusedxml`_ on PyPI has further information about
all known attack vectors with examples and references.

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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Documentation/2024-02-14-20-17-04.gh-issue-115399.fb9a0R.rst
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Document CVE-2023-52425 of Expat <2.6.0 under "XML vulnerabilities".
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