Python Releases For Your Security!

New security releases for 3.10, 3.11 and 3.12 are now available. (As these Python versions are now in security-fix-only mode, these are source-only releases, and there is no pre-set release cadence.)

Security content in these releases

Email and header-related

• gh-144125: email.generator.BytesGenerator now refuses to serialize headers that are unsafely folded or delimited (see email.policy.Policy.verify_generated_headers); addressing CVE-2024-6923.
• gh-143935: Fixed comment folding in modern email policies to prevent header injection when very long non-foldable comment text is wrapped.
• gh-136063: email.message now ensures linear complexity for legacy HTTP parameter parsing.

HTTP, cookies, and URL parsing-related

• gh-143916: wsgiref.headers.Headers now rejects C0 control characters in fields, values, and parameters.
• gh-143919: http.cookies.Morsel now rejects control characters in fields and values.
• gh-143925: data: URL media types now reject control characters.

• gh-144363: Upgraded bundled libexpat to 2.7.4 to fix CVE-2026-24515 and CVE-2026-25210.
• gh-90949: Added Expat allocation-tracker APIs to xml.parsers.expat parser objects to limit memory amplification from malicious XML input; includes mitigation for CVE-2025-59375.
• gh-142145: Removed quadratic behavior in xml.dom.minidom node ID cache clearing.

Denial-of-service hardening

• gh-119342: Fixed a potential memory denial of service in plistlib.
• gh-119451: Fixed a potential memory denial of service in http.client.
• gh-119452: Fixed a potential memory denial of service in http.server (CGI server on Windows).
• gh-136065: Fixed quadratic complexity in os.path.expandvars().

• gh-137836: Hardened html.parser.HTMLParser with support for additional RAWTEXT/PLAINTEXT elements (plaintext, xmp, iframe, noembed, noframes, optional noscript), improving robust handling of hostile markup.

SSL memory-safety fixes

• gh-144833: Fixed a use-after-free in ssl when SSL_new() fails.

Python 3.12.13

python.org/downloads/release/python-31213

Python 3.11.15

Additional fixes in this release (they were already included in a previous 3.12 release):

• gh-120298: Fixed a use-after-free in list rich comparison handling (list_richcompare_impl) for specially crafted concurrent inputs.
• gh-120384: Fixed an out-of-bounds access in list slice assignment (list_ass_subscript) under specially crafted concurrent inputs.

python.org/downloads/release/python-31115

Python 3.10.20

Additional fixes in this release (they were already included in a previous 3.12 release):

• gh-120298: Fixed a use-after-free in list rich comparison handling (list_richcompare_impl) for specially crafted concurrent inputs.
• gh-120384: Fixed an out-of-bounds access in list slice assignment (list_ass_subscript) under specially crafted concurrent inputs.

python.org/downloads/release/python-31020

Stay safe and upgrade!

As always, upgrading is highly recommended to all users of affected versions.

Enjoy the new releases

Thanks to all of the many volunteers who help make Python Development and this release possible! Please consider supporting our efforts by volunteering yourself or through organisation contributions to the Python Software Foundation.

Regards from your security-fix release team, Thomas Wouters Pablo Galindo Salgado