PSF-2026-42

The cleanup of tempfile.TemporaryDirectory is vulnerable to a race condition. An attacker who can modify the tree during cleanup can replace a directory with a symbolic link, causing files outside of the temporary directory to be deleted or have their permissions and file flags reset, with the...

PSF-2026-41

In CPython 3.13 and earlier, the tarfile module's data and tar extraction filters are vulnerable to crafted archives containing a hard link to a symbolic link. Such archives may cause extraction to modify the permissions or modification time of a file outside the destination directory, or expose...

PSF-2026-40

When tarfile extracts a link on a system that doesn't support links, it falls back to extracting a member from the archive. In this case, the filter function is run twice: once for the extracted member, and once with name set to the location of the link. For one of the calls, the return value was...

PSF-2026-39

When decompressing crafted zip files using the bzip/LZMA/Zstandard compressions, Python could use an attacker-controlled size to pre-allocate memory, possibly resulting in memory exhaustion...

PSF-2026-38

The tarfile module's tar and data extraction filters created directories outside the destination for members whose name leaves the destination and returns to it, such as ../evil/../dest/sub/file. The containment check used the resolved path, but intermediate directories were created from the name...

PSF-2026-36

The HTTPPasswordMgr class in the urllib.request module, along with its subclasses HTTPPasswordMgrWithDefaultRealm and HTTPPasswordMgrWithPriorAuth, did not take the URL scheme into account when matching stored credentials against a requested URL. Credentials added for an https:// URL were also us...

PSF-2026-34

Element.findall and fully-consumed Element.iterfind exhibit On^2 time complexity when using XPath index predicates e.g. 1, last, last-N on XML documents with many same-tag siblings. Element.find is only affected when the first match is near the end of the sibling list, such as with last or...

PSF-2026-33

The incremental HTML parser html.parser.HTMLParser allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data...

PSF-2026-32

In the Tarfile.extract function, the filter parameter is not passed properly when extracting hardlinks. An affected system that extracts content from untrusted tar files could end up writing files with an unexpected uid/gid despite the user passing filter='data' to the extract function...

PSF-2026-31

When using the "tarfile" module with a file opened in "streaming mode" mode="r|" the tarfile module did not properly handle EOF, making archive parsing take exponentially longer...

PSF-2026-29

When using the "configparser" module to write configuration files containing multi-line text values with carriage return characters \r the resulting file could be injected with unexpected keys and values if the attacker controls the written value...

PSF-2026-30

tarfile.extractall with the 'data' or 'tar' filter could be bypassed by a crafted archive where a hardlink references a symlink stored at a deeper name than the hardlink itself. The extraction fallback validated the symlink at it's archived location but recreated it at the hardlink's shallower...

PSF-2026-28

To allow builds of Python to be run from an in-tree layout rather than an installed file layout, the VPATH variable is defined at build time and used to locate certain landmarks - specifically, Modules/setup.local. When this landmark is found relative to VPATH relative to the executable, Python...

PSF-2026-27

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...

PSF-2026-26

tarfile.datafilter could be bypassed using crafted link entries, including symlinks with empty or directory-like names, to redirect later archive members outside the intended extraction directory. This allowed a malicious tar archive to cause tarfile.extractall to write files outside the...

PSF-2026-25

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...

PSF-0000-CVE-2026-8328

The ftpcp function in Lib/ftplib.py was not updated when CVE-2021-4189 was fixed. While makepasv was patched to replace server-supplied PASV host addresses with the actual peer address getpeername0, ftpcp still calls parse227 directly and passes the raw attacker-controllable IP address and port t...

PSF-2026-23

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...

PSF-2026-22

If shutil.unpackarchive is given a ZIP archive with an absolute Windows path containing a drive C:\... then the archive will be extracted outside the target directory which is different than other operating systems. Only Windows is affected by this vulnerability...

PSF-2026-21

http.cookies.Morsel.jsoutput returns an inline snippet and only escapes " for JavaScript string context. It does not neutralize the HTML parser-sensitive sequence inside the generated script element. Mitigation base64-encodes the cookie value to disallow escaping using cookie value...

PSF-0000-CVE-2026-3298

The method "sockrecvfrominto" of "asyncio.ProacterEventLoop" Windows only was missing a boundary check for the data buffer when using nbytes parameter. This allowed for an out-of-bounds buffer write if data was larger than the buffer size. Non-Windows platforms are not affected...

PSF-2026-20

The method "sockrecvfrominto" of "asyncio.ProacterEventLoop" Windows only was missing a boundary check for the data buffer when using nbytes parameter. This allowed for an out-of-bounds buffer write if data was larger than the buffer size. Non-Windows platforms are not affected...

PSF-2026-19

The "profiling.sampling" module Python 3.15+ and "asyncio introspection capabilities" 3.14+, "python -m asyncio ps" and "python -m asyncio pstree" features could be used to read and write addresses in a privileged process if that process connected to a malicious or "infected" Python process via t...

PSF-2026-17

Mitgation of CVE-2026-4519 was incomplete. If the URL contained "%action" the mitigation could be bypassed for certain browser types the "webbrowser.open" API could have commands injected into the underlying shell. See CVE-2026-4519 for details...

PSF-0000-CVE-2026-4786

Mitgation of CVE-2026-4519 was incomplete. If the URL contained "%action" the mitigation could be bypassed for certain browser types the "webbrowser.open" API could have commands injected into the underlying shell. See CVE-2026-4519 for details...

PSF-2026-18

Use-after-free UAF was possible in the lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile when a memory allocation fails with a MemoryError and the decompression instance is re-used. This scenario can be triggered if the process is under memory pressure. The fix cleans up the dangling...

PSF-2026-16

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...

PSF-2026-15

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

PSF-2026-14

The webbrowser.open API would accept leading dashes in the URL which could be handled as command line options for certain web browsers. New behavior rejects leading dashes. Users are recommended to sanitize URLs prior to passing to webbrowser.open...

PSF-2026-13

DISPUTED: The project has clarified that the documentation was incorrect, and that pkgutil.getdata has the same security model as open. The documentation has been updated to clarify this point. There is no vulnerability in the function if following the intended security model. pkgutil.getdata did...

PSF-2026-12

When an Expat parser with a registered ElementDeclHandler parses an inline document type definition containing a deeply nested content model a C stack overflow occurs...

PSF-2026-11

The fix for CVE-2026-0672, which rejected control characters in http.cookies.Morsel, was incomplete. The Morsel.update, |= operator, and unpickling paths were not patched, allowing control characters to bypass input validation. Additionally, BaseCookie.jsoutput lacked the output validation applie...

PSF-2026-10

The "tarfile" module would still apply normalization of AREGTYPE \x00 blocks to DIRTYPE, even while processing a multi-block member such as GNUTYPELONGNAME or GNUTYPELONGLINK. This could result in a crafted tar archive being misinterpreted by the tarfile module compared to other implementations...

PSF-2026-9

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...

PSF-2026-8

The email module, specifically the "BytesGenerator" class, didn’t properly quote newlines for email headers when serializing an email message allowing for header injection when an email is serialized. This is only applicable if using "LiteralHeader" writing headers that don't respect email foldin...

PSF-2026-7

When passing data to the b64decode, standardb64decode, and urlsafeb64decode functions in the "base64" module the characters "+/" will always be accepted, regardless of the value of "altchars" parameter, typically used to establish an "alternative base64 alphabet" such as the URL safe alphabet. Th...

PSF-2026-5

When using http.cookies.Morsel, user-controlled cookie values and parameters can allow injecting HTTP headers into messages. Patch rejects all control characters within cookie names, values, and parameters...

PSF-2026-4

The poplib module, when passed a user-controlled command, can have additional commands injected using newlines. Mitigation rejects commands containing control characters...

PSF-2026-3

The imaplib module, when passed a user-controlled command, can have additional commands injected using newlines. Mitigation rejects commands containing control characters...

PSF-2026-2

User-controlled data URLs parsed by urllib.request.DataHandler allow injecting headers through newlines in the data URL mediatype...

PSF-2026-1

When folding a long comment in an email header containing exclusively unfoldable characters, the parenthesis would not be preserved. This could be used for injecting headers into email messages where addresses are user-controlled and not sanitized...

PSF-2025-16

When building nested elements using xml.dom.minidom methods such as appendChild that have a dependency on clearidcache the algorithm is quadratic. Availability can be impacted when building excessively nested documents...

PSF-2025-15

When loading a plist file, the plistlib module reads data in size specified by the file itself, meaning a malicious file can cause OOM and DoS issues...

PSF-2025-14

When reading an HTTP response from a server, if no read amount is specified, the default behavior will be to use Content-Length. This allows a malicious server to cause the client to read large amounts of data into memory, potentially causing OOM or other DoS...

PSF-2025-13

If the value passed to os.path.expandvars is user-controlled a performance degradation is possible when expanding environment variables...

PSF-2025-12

The 'zipfile' module would not check the validity of the ZIP64 End of Central Directory EOCD Locator record offset value would not be used to locate the ZIP64 EOCD record, instead the ZIP64 EOCD record would be assumed to be the previous record in the ZIP archive. This could be abused to create Z...

PSF-2025-11

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...

PSF-2025-5

Allows modifying some file metadata e.g. last modified with filter="data" or file permissions chmod with filter="tar" of files outside the extraction directory. You are affected by this vulnerability if using the tarfile module to extract untrusted tar archives using TarFile.extractall or...

PSF-2025-8

When using a TarFile.errorlevel = 0 and extracting with a filter the documented behavior is that any filtered members would be skipped and not extracted. However the actual behavior of TarFile.errorlevel = 0 in affected versions is that the member would still be extracted and not skipped...

PSF-2025-6

Allows the extraction filter to be ignored, allowing symlink targets to point outside the destination directory, and the modification of some file metadata. You are affected by this vulnerability if using the tarfile module to extract untrusted tar archives using TarFile.extractall or...