Python full changelog

Security:
gh-160300: Fix http.cookiejar.DefaultCookiePolicy accepting and returning cookies with a negative Version attribute without checking their domain against the request host. Such cookies are now ignored.
CVE 2026-114583, gh-160097: tarfile.tar_filter() now rejects link members whose path resolves to the destination directory itself, as tarfile.data_filter() already did.
CVE 2026-115557, gh-160040: ssl now rejects TLS certificate chains that contain any of a set of compromised eMudhra intermediate CA keys. This is an extraordinary measure and a last line of defense: removing trust is primarily the job of the platform root store, and the built-in denylist only blocks connections while that update has not yet reached the OS, a container image, or a bundled trust store in various Python packages. Entries are added to the denylist only under a very high threshold. The denylist matches on the public key (the SHA-256 digest of the RFC 5280 SubjectPublicKeyInfo), so it also covers the cross-signed certificates that reuse one of the distrusted keys.
Core and Builtins:
gh-160491: Fix the location reported for invalid escape sequences in f-strings and t-strings. The SyntaxError now points at the literal part that contains the escape, instead of at the closing quote.
gh-160268: Fix a crash in tokenize when a mismatched closing bracket follows the opening brace of an f-string or t-string replacement field, as in f'{]a'. It now raises the same “unmatched” error as the parser.
gh-106045: Fix venv path discovery when the base executable resolves to a location outside the installation pointed to by the home key in pyvenv.cfg. The standard library is now found from home, and extension modules from the resolved executable’s installation, instead of falling back to the compiled-in prefix.
gh-160162: Fix a crash on 32-bit platforms when left shifting an int by a count close to sys.maxsize * sys.int_info.bits_per_digit. OverflowError is now raised, as for other to

Security:
gh-159894: Bump the version of pip bundled in ensurepip to version 26.2.2.
gh-159428: mimetypes no longer reads the files listed in mimetypes.knownfiles by default on Windows, and uses only the registry.
gh-157953: Update bundled libexpat to version 2.9.0.
Core and Builtins:
gh-159739: Avoid a crash if allocation fails while creating a string.templatelib.Template iterator.
gh-159739: Propagate errors during generic class construction and avoid a crash after failed generic alias substitution.
gh-159739: Raise OverflowError when the absolute value of a dynamic printf-style formatting width is too large.
gh-159739: Fix a reference leak in gc.get_objects() and gc.get_referrers() when an internal allocation fails in the free-threaded build.
gh-159739: Fix memory leaks during interpreter startup when a path configuration file is empty or too large, or when an audit hook rejects a command.
gh-159739: Avoid a crash when an interpreter configuration string cannot be encoded as UTF-8.
gh-159739: Preserve the original SyntaxError if allocating optional error metadata fails.
gh-159739: Avoid a crash if formatting an integer with the c presentation type runs out of memory.
gh-159739: Avoid a crash when a module filename cannot be encoded as UTF-8.
gh-159603: On FreeBSD, call pthread_attr_get_np() to get the stack size (and guard size) of the current thread. Patch by Victor Stinner.
gh-130279: Fix bug where compiler did not set the right exception handler for some jump instructions.
gh-159430: Report the correct exception if looking up __bytes__() raises an exception while performing %-formatting of bytes.
gh-159320: Add dynamic detection of stack sizes on Android, allowing safer deep recursion.
gh-159288: Fix a crash when walking a very long chain of lazy import placeholders, as created by an aliased dotted import such as lazy import a.b.c as d. RecursionError is now raised instead.
gh-159285: Fix a crash in a debug build when copying an empty dict fails with MemoryErr

Security:
gh-157265: In tarfile, when extracting a link falls back to extracting a member of the archive, skip the member when the filter function returns None when called with the extracted member’s name replaced with the link’s.
gh-157579: Fix a race condition in the cleanup of tempfile.TemporaryDirectory. When working around file system permission errors, files are now removed relative to open directory file descriptors instead of resolving their path again, so that replacing a directory of the tree with a symbolic link can no longer make the cleanup delete files outside of the temporary directory. This addresses CVE 2026-12345.
Core and Builtins:
gh-158803: Fix a crash in bytes.join() and bytearray.join() in the free-threaded build when another thread concurrently mutates the list being joined. Patch by Christian Aurich Zanettini Martins.
gh-158592: Skip the array reallocation when shrinking a small list. Patch by Donghee Na.
gh-158583: bytes.fromhex() and bytearray.fromhex(): Fix uninitialized memory read. Patch by Victor Stinner.
gh-158592: del list[index] now triggers shrinking the list’s internal array.
gh-156204: Fix a crash in PyErr_GivenExceptionMatches() when evaluating deeply nested exception tuples. The recursion is now bounded, and exceeding the limit is reported as an unraisable exception.
gh-152075: Reduced lock contention during LOAD_GLOBAL bytecode specialization under free threading.
Library:
gh-87720: Fixed error in email new policies where header folding failed to detect the need to re-quote text obtained from encoded words in certain cases.
gh-158539: Fix macOS runtime section lookup for remote debugging when virtual memory region sizes differ from Mach-O segment file sizes.
gh-156321: Fix asyncio.shield() reporting an exception from the inner future through the loop exception handler as soon as it completes after the shield was cancelled, even when the exception is retrieved afterwards. The exception is now reported only if it is never

Python 3.14.8 is an expedited security release and the eighth maintenance release of 3.14, containing around 354 bugfixes, build improvements and documentation changes from 142 contributors since 3.14.7
Security content in this releases:
CVE-2026-19445 gh-156293 Use-after-free of a server-side SSLContext when sni_callback switches contexts
CVE-2026-19553 gh-156793 SSLContext.wrap_bio() missing validation of server_hostname parameter
CVE-2026-82049 gh-157190 tarfile extraction filters allow file modification and content disclosure via hard link to symlink
CVE-2026-15310 gh-156002 Memory exhaustion in zipfile in bzip2/LZMA/Zstandard decompression
CVE-2026-19672 gh-155999 tarfile extraction filter bypass allows creation of directories outside the destination
CVE-2026-15806 gh-155694 urllib.request.HTTPPasswordMgr credentials for one URL scheme sent over another scheme
CVE-2026-17084 gh-155292 StringPrep algorithm considered Unicode codepoint attributes outside Unicode 3.2.0
gh-158446 Reject float format precision near INT_MAX
gh-157953 Update bundled Expat to 2.8.5
gh-158010 Update bundled OpenSSL to 3.5.9 for Windows, macOS, Android and iOS
New features:
PEP 779: Free-threaded Python is officially supported
PEP 649: The evaluation of annotations is now deferred, improving the semantics of using annotations.
PEP 750: Template string literals (t-strings) for custom string processing, using the familiar syntax of f-strings.
PEP 734: Multiple interpreters in the stdlib.
PEP 784: A new module compression.zstd providing support for the Zstandard compression algorithm.
PEP 758: except and except* expressions may now omit the brackets.
Syntax highlighting in PyREPL, and support for color in unittest, argparse, json and calendar CLIs.
PEP 768: A zero-overhead external debugger interface for CPython.
UUID versions 6-8 are now supported by the uuid module, and generation of versions 3-5 are up to 40% faster.
PEP 765: Disallow return/break/continue that exit a finally block.
PEP

Security:
gh-145986: xml.parsers.expat: Fixed a crash caused by unbounded C recursion when converting deeply nested XML content models with ElementDeclHandler(). This addresses CVE 2026-4224.
gh-145599: Reject control characters in http.cookies.Morsel update() and js_output(). This addresses CVE 2026-3644.
gh-145506: Fixes CVE 2026-2297 by ensuring that SourcelessFileLoader uses io.open_code() when opening .pyc files.
gh-144370: Disallow usage of control characters in status in wsgiref.handlers to prevent HTTP header injections. Patch by Benedikt Johannes.
gh-143930: Reject leading dashes in URLs passed to webbrowser.open().
Core and Builtins:
gh-148157: Fix an unlikely crash when parsing an invalid type comments for function parameters. Found by OSS Fuzz in #492782951.
gh-148144: Initialize _PyInterpreterFrame.visited when copying interpreter frames so incremental GC does not read an uninitialized byte from generator and frame-object copies.
gh-146615: Fix a crash in __get__() for METH_METHOD descriptors when an invalid (non-type) object is passed as the second argument. Patch by Steven Sun.
gh-146308: Fixed several error handling issues in the _remote_debugging module, including safer validation of remote int objects, clearer asyncio task chain failures, and cache cleanup fixes that avoid leaking or double-freeing metadata on allocation failure. Patch by Pablo Galindo.
gh-146128: Fix a bug which could cause constant values to be partially corrupted in AArch64 JIT code. This issue is theoretical, and hasn’t actually been observed in unmodified Python interpreters.
gh-146250: Fixed a memory leak in SyntaxError when re-initializing it.
gh-146245: Fixed reference leaks in socket when audit hooks raise exceptions in socket.getaddrinfo() and socket.sendto().
gh-146196: Fix potential Undefined Behavior in PyUnicodeWriter_WriteASCII() by adding a zero-length check. Patch by Shamil Abdulaev.
gh-146227: Fix wrong type in _Py_atomic_load_uint16 in the C11 atomics backend (

New features:
PEP 779: Free-threaded Python is officially supported
PEP 649: The evaluation of annotations is now deferred, improving the semantics of using annotations.
PEP 750: Template string literals (t-strings) for custom string processing, using the familiar syntax of f-strings.
PEP 734: Multiple interpreters in the stdlib.
PEP 784: A new module compression.zstd providing support for the Zstandard compression algorithm.
PEP 758: except and except* expressions may now omit the brackets.
Syntax highlighting in PyREPL, and support for color in unittest, argparse, json and calendar CLIs.
PEP 768: A zero-overhead external debugger interface for CPython.
UUID versions 6-8 are now supported by the uuid module, and generation of versions 3-5 are up to 40% faster.
PEP 765: Disallow return/break/continue that exit a finally block.
PEP 741: An improved C API for configuring Python.
A new type of interpreter. For certain newer compilers, this interpreter provides significantly better performance. Opt-in for now, requires building from source.
Improved error messages.
Builtin implementation of HMAC with formally verified code from the HACL* project.
A new command-line interface to inspect running Python processes using asynchronous tasks.
The pdb module now supports remote attaching to a running Python process.
Build changes:
PEP 761: Python 3.14 and onwards no longer provides PGP signatures for release artifacts. Instead, Sigstore is recommended for verifiers.
Official macOS and Windows release binaries include an experimental JIT compiler.
Official Android binary releases are now available.

A new high-frequency, low-overhead, statistical sampling profiler and dedicated profiling package
Python now uses UTF-8 as the default encoding
A new PyBytesWriter C API to create a Python bytes object
Improved error messages

gh-139573: Updated bundled version of OpenSSL to 3.0.18.
Tools/Demos:
gh-139330: SBOM generation tool didn’t cross-check the version and checksum values against the Modules/expat/refresh.sh script, leading to the values becoming out-of-date during routine updates.
gh-132006: XCframeworks now include privacy manifests to satisfy Apple App Store submission requirements.
gh-138171: A script for building an iOS XCframework was added. As part of this change, the top level iOS folder has been moved to be a subdirectory of the Apple folder.
Security:
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.
Library:
gh-139312: Upgrade bundled libexpat to 2.7.3