PSF-2022-2 Buffer overflow vulnerability in os.symlink on Windows

Python Software Foundation CPython version From 3.2 until 3.6.4 on Windows contains a Buffer Overflow vulnerability in os.symlink function on Windows that can result in Arbitrary code execution, likely escalation of privilege. This attack appears to be exploitable via a python script that creates...

PSF-2020-8 urllib basic auth regex denial of service

Python 2.7 through 2.7.17, 3.5 through 3.5.9, 3.6 through 3.6.10, 3.7 through 3.7.6, and 3.8 through 3.8.1 allows an HTTP server to conduct Regular Expression Denial of Service ReDoS attacks against a client because of urllib.request.AbstractBasicAuthHandler catastrophic backtracking...

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-2019-4 Windows: vulnerable bzip2 1.0.6

BZ2decompress in decompress.c in bzip2 through 1.0.6 has an out-of-bounds write when there are many selectors...

PSF-2018-4 difflib and poplib catastrophic backtracking

python before versions 2.7.15, 3.4.9, 3.5.6rc1, 3.6.5rc1 and 3.7.0 is vulnerable to catastrophic backtracking in the difflib.ISLINEJUNK method. An attacker could use this flaw to cause denial of service...

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-2026-19

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-2024-9

There is a LOW severity vulnerability affecting CPython, specifically the 'http.cookies' standard library module. When parsing cookies that contained backslashes for quoted characters in the cookie value, the parser would use an algorithm with quadratic complexity, resulting in excess CPU resourc...

PSF-2023-12 Groups not dropped before running subprocess when using empty 'extra_groups' parameter

An issue was found in CPython 3.12.0 subprocess module on POSIX platforms. The issue was fixed in CPython 3.12.1 and does not affect other stable releases. When using the extragroups= parameter with an empty list as a value ie extragroups= the logic regressed to not call setgroups0, NULL before...

PSF-2023-8 Bypass TLS handshake on closed sockets

Instances of ssl.SSLSocket are 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. The vulnerability is caused when a socket is connected, data is sent by the malicio...

PSF-2022-4 Prevent DoS by large str-int conversions

A flaw was found in python. In algorithms with quadratic time complexity using non-binary bases, when using int"text", a system could take 50ms to parse an int string with 100,000 digits and 5s for 1,000,000 digits float, decimal, int.frombytes, and int for binary bases 2, 4, 8, 16, and 32 are no...

PSF-2021-1 urllib parse_qsl(): Web cache poisoning - semicolon as a query args separator

The package python/cpython from 0 and before 3.6.13, from 3.7.0 and before 3.7.10, from 3.8.0 and before 3.8.8, from 3.9.0 and before 3.9.2 are vulnerable to Web Cache Poisoning via urllib.parse.parseqsl and urllib.parse.parseqs by using a vector called parameter cloaking. When the attacker can...

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-2026-28

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-2026-20

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-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-2024-3

On Windows a directory returned by tempfile.mkdtemp would not always have permissions set to restrict reading and writing to the temporary directory by other users, instead usually inheriting the correct permissions from the default location. Alternate configurations or users without a profile...

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-2026-15

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-2025-3

During an address list folding when a separating comma ends up on a folded line and that line is to be unicode-encoded then the separator itself is also unicode-encoded. Expected behavior is that the separating comma remains a plan comma. This can result in the address header being misinterpreted...

PSF-2022-8 urllib.parse should sanitize urls containing ASCII newline and tabs.

A flaw was found in Python, specifically within the urllib.parse module. This module helps break Uniform Resource Locator URL strings into components. The issue involves how the urlparse method does not sanitize input and allows characters like '\r' and '\n' in the URL path. This flaw allows an...

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-2024-4

A defect was discovered in the Python “ssl” module where there is a memory race condition with the ssl.SSLContext methods “certstorestats” and “getcacerts”. The race condition can be triggered if the methods are called at the same time as certificates are loaded into the SSLContext, such as durin...

PSF-2020-1 xmlrpc gzip unlimited read

The gzipdecode function in the xmlrpc client library in Python 3.4 and earlier allows remote attackers to cause a denial of service memory consumption via a crafted HTTP request...

PSF-2018-3 difflib and poplib catastrophic backtracking

python before versions 2.7.15, 3.4.9, 3.5.6rc1, 3.6.5rc1 and 3.7.0 is vulnerable to catastrophic backtracking in pop3lib's apop method. An attacker could use this flaw to cause denial of service...

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-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-2025-1

The Python standard library functions urllib.parse.urlsplit and urlparse accepted domain names that included square brackets which isn't valid according to RFC 3986. Square brackets are only meant to be used as delimiters for specifying IPv6 and IPvFuture hosts in URLs. This could result in...

PSF-CVE-2023-6507 Groups not dropped before running subprocess when using empty 'extra_groups' parameter

An issue was found in CPython 3.12.0 subprocess module on POSIX platforms. The issue was fixed in CPython 3.12.1 and does not affect other stable releases. When using the extragroups= parameter with an empty list as a value ie extragroups= the logic regressed to not call setgroups0, NULL before...

PSF-2017-5 Zlib 1.2.11

The crc32big function in crc32.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact via vectors involving big-endian CRC calculation...

PSF-0000-CVE-2026-82049

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-2026-11

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-2024-5

The “ipaddress” module contained incorrect information about whether certain IPv4 and IPv6 addresses were designated as “globally reachable” or “private”. This affected the isprivate and isglobal properties of the ipaddress.IPv4Address, ipaddress.IPv4Network, ipaddress.IPv6Address, and...

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-2026-23

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-2023-4

The legacy email.utils.parseaddr function in Python through 3.11.4 allows attackers to trigger "RecursionError: maximum recursion depth exceeded while calling a Python object" via a crafted argument. This argument is plausibly an untrusted value from an application's input data that was supposed ...

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-2026-12

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-2024-12

A vulnerability has been found in the CPython venv module and CLI where path names provided when creating a virtual environment were not quoted properly, allowing the creator to inject commands into virtual environment "activation" scripts ie "source venv/bin/activate". This means that...

PSF-2024-10

There is a HIGH severity vulnerability affecting the CPython "zipfile" module affecting "zipfile.Path". Note that the more common API "zipfile.ZipFile" class is unaffected. When iterating over names of entries in a zip archive for example, methods of "zipfile.Path" like "namelist", "iterdir", etc...

PSF-2024-2

An issue was found in the CPython zipfile module affecting versions 3.12.1, 3.11.7, 3.10.13, 3.9.18, and 3.8.18 and prior. The zipfile module is vulnerable to “quoted-overlap” zip-bombs which exploit the zip format to create a zip-bomb with a high compression ratio. The fixed versions of CPython...

PSF-2017-3 Zlib 1.2.11

inffast.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact by leveraging improper pointer arithmetic...

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-2007-2 Directory path traversal in extract() and extractall() tarfile functions via '..' (dot dot) sequences

Directory traversal vulnerability in the 1 extract and 2 extractall functions in the tarfile module in Python allows user-assisted remote attackers to overwrite arbitrary files via a .. dot dot sequence in filenames in a TAR archive, a related issue to CVE-2001-1267...

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-2024-7

The “socket” module provides a pure-Python fallback to the socket.socketpair function for platforms that don’t support AFUNIX, such as Windows. This pure-Python implementation uses AFINET or AFINET6 to create a local connected pair of sockets. The connection between the two sockets was not verifi...

PSF-2026-35

Attacker-controlled CSV samples can trigger super-linear regular-expression work during dialect sniffing and consume significant CPU when applications pass unbounded input to csv.Sniffer.sniff...

PSF-2020-7 CVE-2020-8315: Unsafe DLL loading in getpathp.c on Windows 7

In Python CPython 3.6 through 3.6.10, 3.7 through 3.7.6, and 3.8 through 3.8.1, an insecure dependency load upon launch on Windows 7 may result in an attacker's copy of api-ms-win-core-path-l1-1-0.dll being loaded and used instead of the system's copy. Windows 8 and later are unaffected...