Changelog¶

Security¶

• gh-139700: Check consistency of the zip64 end of central directory record. Support records with “zip64 extensible data” if there are no bytes prepended to the ZIP file.

• gh-139400: xml.parsers.expat: Make sure that parent Expat parsers are only garbage-collected once they are no longer referenced by subparsers created by ExternalEntityParserCreate(). Patch by Sebastian Pipping.

• gh-135661: Fix parsing start and end tags in html.parser.HTMLParser according to the HTML5 standard.

  • Whitespaces no longer accepted between </ and the tag name. E.g. </ script> does not end the script section.

  • Vertical tabulation (\v) and non-ASCII whitespaces no longer recognized as whitespaces. The only whitespaces are \t\n\r\f and space.

  • Null character (U+0000) no longer ends the tag name.

  • Attributes and slashes after the tag name in end tags are now ignored, instead of terminating after the first > in quoted attribute value. E.g. </script/foo=">"/>.

  • Multiple slashes and whitespaces between the last attribute and closing > are now ignored in both start and end tags. E.g. <a foo=bar/ //>.

  • Multiple = between attribute name and value are no longer collapsed. E.g. <a foo==bar> produces attribute “foo” with value “=bar”.

• gh-135661: Fix CDATA section parsing in html.parser.HTMLParser according to the HTML5 standard: ] ]> and ]] > no longer end the CDATA section. Add private method _set_support_cdata() which can be used to specify how to parse <[CDATA[ — as a CDATA section in foreign content (SVG or MathML) or as a bogus comment in the HTML namespace.

• gh-102555: Fix comment parsing in html.parser.HTMLParser according to the HTML5 standard. --!> now ends the comment. -- > no longer ends the comment. Support abnormally ended empty comments <--> and <--->.

• gh-135462: Fix quadratic complexity in processing specially crafted input in html.parser.HTMLParser. End-of-file errors are now handled according to the HTML5 specs – comments and declarations are automatically closed, tags are ignored.

• gh-118350: Fix support of escapable raw text mode (elements “textarea” and “title”) in html.parser.HTMLParser.

• gh-86155: html.parser.HTMLParser.close() no longer loses data when the <script> tag is not closed. Patch by Waylan Limberg.

Library¶

• gh-139312: Upgrade bundled libexpat to 2.7.3

• gh-138998: Update bundled libexpat to 2.7.2

• gh-130577: tarfile now validates archives to ensure member offsets are non-negative. (Contributed by Alexander Enrique Urieles Nieto in gh-130577.)

• gh-135374: Update the bundled copy of setuptools to 79.0.1.

Security¶

• gh-135034: Fixes multiple issues that allowed tarfile extraction filters (filter="data" and filter="tar") to be bypassed using crafted symlinks and hard links.

  Addresses CVE 2024-12718, CVE 2025-4138, CVE 2025-4330, and CVE 2025-4517.

• gh-133767: Fix use-after-free in the “unicode-escape” decoder with a non-“strict” error handler.

• gh-128840: Short-circuit the processing of long IPv6 addresses early in ipaddress to prevent excessive memory consumption and a minor denial-of-service.

Library¶

• gh-128840: Fix parsing long IPv6 addresses with embedded IPv4 address.

• gh-134062: ipaddress: fix collisions in __hash__() for IPv4Network and IPv6Network objects.

• gh-123409: Fix ipaddress.IPv6Address.reverse_pointer output according to RFC 3596, §2.5. Patch by Bénédikt Tran.

• bpo-43633: Improve the textual representation of IPv4-mapped IPv6 addresses (RFC 4291 Sections 2.2, 2.5.5.2) in ipaddress. Patch by Oleksandr Pavliuk.

Security¶

• gh-131809: Update bundled libexpat to 2.7.1

• gh-131261: Upgrade to libexpat 2.7.0

• gh-105704: When using urllib.parse.urlsplit() and urllib.parse.urlparse() host parsing would not reject domain names containing square brackets ([ and ]). Square brackets are only valid for IPv6 and IPvFuture hosts according to RFC 3986 Section 3.2.2.

• gh-121284: Fix bug in the folding of rfc2047 encoded-words when flattening an email message using a modern email policy. Previously when an encoded-word was too long for a line, it would be decoded, split across lines, and re-encoded. But commas and other special characters in the original text could be left unencoded and unquoted. This could theoretically be used to spoof header lines using a carefully constructed encoded-word if the resulting rendered email was transmitted or re-parsed.

• gh-80222: Fix bug in the folding of quoted strings when flattening an email message using a modern email policy. Previously when a quoted string was folded so that it spanned more than one line, the surrounding quotes and internal escapes would be omitted. This could theoretically be used to spoof header lines using a carefully constructed quoted string if the resulting rendered email was transmitted or re-parsed.

• gh-119511: Fix a potential denial of service in the imaplib module. When connecting to a malicious server, it could cause an arbitrary amount of memory to be allocated. On many systems this is harmless as unused virtual memory is only a mapping, but if this hit a virtual address size limit it could lead to a MemoryError or other process crash. On unusual systems or builds where all allocated memory is touched and backed by actual ram or storage it could’ve consumed resources doing so until similarly crashing.

Library¶

• gh-127257: In ssl, system call failures that OpenSSL reports using ERR_LIB_SYS are now raised as OSError.

Documentation¶

• gh-121277: Writers of CPython’s documentation can now use next as the version for the versionchanged, versionadded, deprecated directives.

Tests¶

• gh-125041: Re-enable skipped tests for zlib on the s390x architecture: only skip checks of the compressed bytes, which can be different between zlib’s software implementation and the hardware-accelerated implementation.

• gh-109396: Fix test_socket.test_hmac_sha1() in FIPS mode. Use a longer key: FIPS mode requires at least of at least 112 bits. The previous key was only 32 bits. Patch by Victor Stinner.

Security¶

• gh-126623: Upgrade libexpat to 2.6.4

• gh-122792: Changed IPv4-mapped ipaddress.IPv6Address to consistently use the mapped IPv4 address value for deciding properties. Properties which have their behavior fixed are is_multicast, is_reserved, is_link_local, is_global, and is_unspecified.

Library¶

• gh-124651: Properly quote template strings in venv activation scripts.

• gh-103848: Add checks to ensure that [ bracketed ] hosts found by urllib.parse.urlsplit() are of IPv6 or IPvFuture format.

Windows¶

• gh-119690: Fixes data type confusion in audit events raised by _winapi.CreateFile and _winapi.CreateNamedPipe.

• gh-116773: Fix instances of <_overlapped.Overlapped object at 0xXXX> still has pending operation at deallocation, the process may crash.

Tests¶

• gh-112769: The tests now correctly compare zlib version when zlib.ZLIB_RUNTIME_VERSION contains non-integer suffixes. For example zlib-ng defines the version as 1.3.0.zlib-ng.

• gh-117187: Fix XML tests for vanilla Expat <2.6.0.

• gh-100454: Fix SSL tests CI for OpenSSL 3.1+

Security¶

• gh-123678: Upgrade libexpat to 2.6.3

• gh-121957: Fixed missing audit events around interactive use of Python, now also properly firing for python -i, as well as for python -m asyncio. The event in question is cpython.run_stdin.

• gh-122133: Authenticate the socket connection for the socket.socketpair() fallback on platforms where AF_UNIX is not available like Windows.

  Patch by Gregory P. Smith <greg@krypto.org> and Seth Larson <seth@python.org>. Reported by Ellie <el@horse64.org>

• gh-121285: Remove backtracking from tarfile header parsing for hdrcharset, PAX, and GNU sparse headers.

• gh-118486: os.mkdir() on Windows now accepts mode of 0o700 to restrict the new directory to the current user. This fixes CVE-2024-4030 affecting tempfile.mkdtemp() in scenarios where the base temporary directory is more permissive than the default.

• gh-116741: Update bundled libexpat to 2.6.2

Library¶

• gh-123693: Use platform-agnostic behavior when computing zipfile.Path.name.

• gh-123270: Applied a more surgical fix for malformed payloads in zipfile.Path causing infinite loops (gh-122905) without breaking contents using legitimate characters.

• gh-123067: Fix quadratic complexity in parsing "-quoted cookie values with backslashes by http.cookies.

• gh-122905: zipfile.Path objects now sanitize names from the zipfile.

• gh-121650: email headers with embedded newlines are now quoted on output. The generator will now refuse to serialize (write) headers that are unsafely folded or delimited; see verify_generated_headers. (Contributed by Bas Bloemsaat and Petr Viktorin in gh-121650.)

• gh-113171: Fixed various false positives and false negatives in

  • ipaddress.IPv4Address.is_private (see these docs for details)

  • ipaddress.IPv4Address.is_global

  • ipaddress.IPv6Address.is_private

  • ipaddress.IPv6Address.is_global

  Also in the corresponding ipaddress.IPv4Network and ipaddress.IPv6Network attributes.

• gh-102988: email.utils.getaddresses() and email.utils.parseaddr() now return ('', '') 2-tuples in more situations where invalid email addresses are encountered instead of potentially inaccurate values. Add optional strict parameter to these two functions: use strict=False to get the old behavior, accept malformed inputs. getattr(email.utils, 'supports_strict_parsing', False) can be use to check if the strict paramater is available. Patch by Thomas Dwyer and Victor Stinner to improve the CVE-2023-27043 fix.

• gh-67693: Fix urllib.parse.urlunparse() and urllib.parse.urlunsplit() for URIs with path starting with multiple slashes and no authority. Based on patch by Ashwin Ramaswami.

Core and Builtins¶

• gh-112275: A deadlock involving pystate.c’s HEAD_LOCK in posixmodule.c at fork is now fixed. Patch by ChuBoning based on previous Python 3.12 fix by Victor Stinner.

Security¶

• gh-115398: Allow controlling Expat >=2.6.0 reparse deferral (CVE-2023-52425) by adding five new methods:

  • xml.etree.ElementTree.XMLParser.flush()

  • xml.etree.ElementTree.XMLPullParser.flush()

  • xml.parsers.expat.xmlparser.GetReparseDeferralEnabled()

  • xml.parsers.expat.xmlparser.SetReparseDeferralEnabled()

  • xml.sax.expatreader.ExpatParser.flush()

• gh-115399: Update bundled libexpat to 2.6.0

• gh-114572: ssl.SSLContext.cert_store_stats() and ssl.SSLContext.get_ca_certs() now correctly lock access to the certificate store, when the ssl.SSLContext is shared across multiple threads.

• gh-113659: Skip .pth files with names starting with a dot or hidden file attribute.

Core and Builtins¶

• gh-102388: Fix a bug where iso2022_jp_3 and iso2022_jp_2004 codecs read out of bounds

Library¶

• gh-115197: urllib.request no longer resolves the hostname before checking it against the system’s proxy bypass list on macOS and Windows.

• gh-115133: Fix tests for XMLPullParser with Expat 2.6.0.

• gh-81194: Fix a crash in socket.if_indextoname() with specific value (UINT_MAX). Fix an integer overflow in socket.if_indextoname() on 64-bit non-Windows platforms.

• gh-109858: Protect zipfile from “quoted-overlap” zipbomb. It now raises BadZipFile when try to read an entry that overlaps with other entry or central directory.

• gh-91133: Fix a bug in tempfile.TemporaryDirectory cleanup, which now no longer dereferences symlinks when working around file system permission errors.

Documentation¶

• gh-115399: Document CVE-2023-52425 of Expat <2.6.0 under “XML vulnerabilities”.

Windows¶

• gh-111239: Update Windows builds to use zlib v1.3.1.

• gh-109991: Windows builds now use OpenSSL 1.1.1w. Note that OpenSSL 1.1 has reached its end of life and no future fixes will be made, and this version of Python is no longer receiving maintenance fixes and will not be updated to OpenSSL 3.0.

Tools/Demos¶

• gh-109991: Update GitHub CI workflows to use OpenSSL 3.0.11 and multissltests to use 1.1.1w, 3.0.11, and 3.1.3.

Security¶

• gh-108310: Fixed an issue where instances of ssl.SSLSocket were vulnerable to a bypass of the TLS handshake and included protections (like certificate verification) and treating sent unencrypted data as if it were post-handshake TLS encrypted data. Security issue reported as CVE-2023-40217 by Aapo Oksman. Patch by Gregory P. Smith.

Library¶