Last updated 6 July 2026

bz2.BZ2Decompressor objects could be reused after a decompression error. If an application caught the resulting OSError and retried with the same decompressor, crafted input could cause the decompressor to resume from an invalid internal state and perform out-of-bounds writes to a stack buffer. This could crash the process when processing untrusted data.

Last updated 6 July 2026

Incomplete mitigation of CVE-2026-4519, %action expansion for command injection to webbrowser.open()

xml.parsers.expat and xml.etree.ElementTree use insufficient entropy for Expat hash-flooding protection, which allows a crafted XML document to trigger hash flooding.\r\n\r\nFully mitigating this vulnerability requires both updating libexpat to 2.8.0 or later and applying this patch.

When calling base64.b64decode() or related functions the decoding process would stop after encountering the first padded quad regardless of whether there was more information to be processed. This can lead to data being accepted which may be processed differently by other implementations. Use "validate=True" to enable stricter processing of base64 data.

CR/LF bytes were not rejected by HTTP client proxy tunnel headers or host.

Last updated 6 July 2026

There is a MEDIUM severity vulnerability affecting CPython.

The email module didn’t properly quote newlines for email headers when serializing an email message allowing for header injection when an email is serialized.

A Denial of Service (DoS) vulnerability exists in the jaraco/zipp library, affecting all versions prior to 3.19.1. The vulnerability is triggered when processing a specially crafted zip file that leads to an infinite loop. This issue also impacts the zipfile module of CPython, as features from the third-party zipp library are later merged into CPython, and the affected code is identical in both projects. The infinite loop can be initiated through the use of functions affecting the Path module in both zipp and zipfile, such as joinpath, the overloaded division operator, and iterdir. Although the infinite loop is not resource exhaustive, it prevents the application from responding. The vulnerability was addressed in version 3.19.1 of jaraco/zipp.

There is a defect in the CPython “tarfile” module affecting the “TarFile” extraction and entry enumeration APIs. The tar implementation would process tar archives with negative offsets without error, resulting in an infinite loop and deadlock during the parsing of maliciously crafted tar archives.

This vulnerability can be mitigated by including the following patch after importing the “tarfile” module:

import tarfile

def blockpatched(self, count): if count < 0: # pragma: no cover raise tarfile.InvalidHeaderError("invalid offset") return blockpatched.origblock(self, count)

blockpatched.origblock = tarfile.TarInfo.block tarfile.TarInfo.block = blockpatched

The import hook in CPython that handles legacy .pyc files (SourcelessFileLoader) is incorrectly handled in FileLoader (a base class) and so does not use io.opencode() to read the .pyc files. sys.audit handlers for this audit event therefore do not fire.

-------- Forwarded Message -------- Date: Fri, 10 Apr 2026 18:19:00 +0000 From: Seth Larson <seth () python org> Reply-To: security-sig () python org To: security-announce () python org

There is a MEDIUM severity vulnerability affecting {project}. Please see the linked CVE ID for the latest information on affected versions:

https://www.cve.org/CVERecord?id=CVE-2026-34460 https://github.com/python/cpython/pull/145267

Security-announce mailing list -- security-announce () python org To unsubscribe send an email to security-announce-leave () python org https://mail.python.org/mailman3//lists/security-announce.python.org

-------- Forwarded Message -------- Date: Mon, 27 Apr 2026 20:48:33 +0000 From: Seth Larson <seth () python org> Reply-To: security-sig () python org To: security-announce () python org

There is a MEDIUM severity vulnerability affecting CPython. Please see the linked CVE ID for the latest information on affected versions:

https://www.cve.org/CVERecord?id=CVE-2026-3087 https://github.com/python/cpython/pull/146591

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-------- Forwarded Message -------- Subject: [Security-announce][CVE-2026-7210] The expat and elementtree parsers use insufficient entropy for XML hash-flooding protection Date: Mon, 11 May 2026 17:58:49 +0100 From: Stan Ulbrych via Security-announce <security-announce () python org> Reply-To: security-sig () python org To: security-announce () python org CC: Stan Ulbrych <stanulbrych () gmail com>

There is a MEDIUM severity vulnerability affecting CPython.

xml.parsers.expat and xml.etree.ElementTree use insufficient entropy for Expat hash-flooding protection, which allows a crafted XML document to trigger hash flooding.

Fully mitigating this vulnerability requires both updating libexpat to 2.8.0 or later and applying this patch.

Please see the linked CVE ID for the latest information on affected versions:

https://www.cve.org/CVERecord?id=CVE-2026-7210 https://github.com/python/cpython/pull/149023

Best regards,  Stan Ulbrych. Security-announce mailing list -- security-announce () python org To unsubscribe send an email to security-announce-leave () python org https://mail.python.org/mailman3//lists/security-announce.python.org

-------- Forwarded Message -------- Date: Wed, 3 Jun 2026 14:56:33 +0100 From: Stan Ulbrych via Security-announce <security-announce () python org> Reply-To: security-sig () python org To: security-announce () python org CC: Stan Ulbrych <stanulbrych () gmail com>

There is a MEDIUM severity vulnerability affecting CPython.

unicodedata.normalize() can take excessive CPU time when processing specially crafted Unicode input containing long runs of combining characters with alternating Canonical Combining Class values. This affects all normalization forms.

Please see the linked CVE ID for the latest information on affected versions:

https://www.cve.org/CVERecord?id=CVE-2026-3276 https://github.com/python/cpython/pull/149080

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-------- Forwarded Message -------- Date: Tue, 16 Jun 2026 16:01:03 +0100 From: Steve Dower <steve.dower () python org> Reply-To: security-sig () python org To: security-announce () python org

Reported by Jake Yamaki, Senior Consultant, Bishop Fox.

Please see the linked CVE ID for the latest information on affected versions:

https://www.cve.org/CVERecord?id=CVE-2026-12003 https://github.com/python/cpython/pull/151545 Security-announce mailing list -- security-announce () python org https://mail.python.org/mailman3//lists/security-announce.python.org