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Critical 9.4
Distrust compromised intermediate certificates in ssl module
Python has added a denylist for known compromised certificates to the "ssl" module to ensure user safety even without certificate revocation configured. Known compromised certificates will automatically be rejected regardless of the SSLContext policy configur…
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Medium 6.9
tar filter allows writing outside destination via empty-named symlink
tarfile.tar_filter 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.extracta…
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High 7.6
SSLContext.wrap_bio() missing validation of server_hostname parameter
ssl.SSLContext.wrap_bio() didn't require the server_hostname argument to not be None if ssl.SSLContext.check_hostname was set. Due to a missing parameter check in SSLObject, if the server_hostname argument isn't supplied then hostname verification would be si…
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Critical 9.2
Use-after-free of a server-side SSLContext when sni_callback switches contexts
A remote, unauthenticated TLS client can make a server crash or call through a freed pointer if its sni_callback assigns a different context to SSLSocket.context (the documented way to select a certificate per server name) and nothing else keeps the original …
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Medium 5.9
Race condition in tempfile.TemporaryDirectory cleanup allows deleting files outside the temporary directory
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 permiss…
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High 8.4
tarfile extraction filters allow file modification and content disclosure via hard link to symlink
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…
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Medium 5.7
tarfile hardlink fallback ignores custom extraction filter rejection via None
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 …
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Low 2.1
zipfile: bzip2/LZMA/Zstandard members decompress without a max_length bound, defeating chunked-read memory limits
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.
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Medium 6.3
tarfile extraction filter bypass allows creation of directories outside the destination
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 …
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Medium 6.0
`HTTPPasswordMgr` can send saved HTTPS credentials via HTTP because of incorrect scheme matching
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 …
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Medium 6.0
stringprep.map_table_b2() deviates from RFC 3454 Table B.2
The "stringprep" module didn't process characters from RFC 3454 tables B.2 or B.3 correctly: the latest Unicode codepoint attributes were used instead of the specified Unicode 3.2.0. This behavior would cause mismatches when processing domain names using IDNA…
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Low 2.0
Quadratic Behavior in xml.etree.ElementPath Index Predicates
`Element.findall()` and fully-consumed `Element.iterfind()` exhibit `O(n^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 firs…
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High 8.7
Incremental HTMLParser feed() allows CPU-exhaustion DoS via repeated unterminated markup declarations
The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.
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Low 2.0
Tarfile.extract() doesn't fully respect filter parameter
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='…
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High 8.2
tarfile opened in streaming mode mishandles EOF
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.
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Medium 4.1
Configuration Injection via Carriage Return (\r) in write() method
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.
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High 7.8
tarfile extraction filter bypass allows escaping the destination directory
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 re…
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High 8.2
bz2.BZ2Decompressor reuse after error can cause a stack buffer overflow
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…
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Medium 6.9
tarfile.data_filter path traversal bypass allows writing outside the extraction directory
tarfile.data_filter 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.extract…
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Medium 6.3
Potential DoS via quadratic complexity in unicodedata.normalize()
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.
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Medium 5.9
FTP PASV SSRF, ftpcp() does not use actual peer address, trusts server-supplied PASV host address
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 (getpeername()[0]), ftpcp() still calls parse227() directly and passes…
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Medium 6.3
The expat and elementtree parsers use insufficient entropy for XML hash-flooding protection
`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 l…
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High 7.0
Incomplete mitigation of CVE-2026-4519, %action expansion for command injection to webbrowser.open()
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.
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Critical 9.1
Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure
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 …
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Medium 5.7
HTTP client proxy tunnel headers not validated for CR/LF
CR/LF bytes were not rejected by HTTP client proxy tunnel headers or host.
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High 7.0
webbrowser.open() allows leading dashes in URLs
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().
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Medium 6.0
Stack overflow parsing XML with deeply nested DTD content models
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.
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Medium 6.0
Incomplete control character validation in http.cookies
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.js_o…
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Medium 5.7
SourcelessFileLoader does not use io.open_code()
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.open_code() to read the .pyc files. sys.audit handlers for this audit event therefore do not fire.
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Medium 5.9
IMAP command injection in user-controlled commands
The imaplib module, when passed a user-controlled command, can have additional commands injected using newlines. Mitigation rejects commands containing control characters.
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Medium 5.3
Bypass extraction filter to modify file metadata outside extraction directory
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 ar…
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High 7.5
Bypassing extraction filter to create symlinks to arbitrary targets outside extraction directory
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 u…
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High 7.5
Extraction filter bypass for linking outside extraction directory
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 u…
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Critical 9.4
Arbitrary writes via tarfile realpath overflow
Allows arbitrary filesystem writes outside the extraction directory during extraction with filter="data". You are affected by this vulnerability if using the tarfile module to extract untrusted tar archives using TarFile.extractall() or TarFile.extract() usin…
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Medium 5.9
Use-after-free in "unicode_escape" decoder with error handler
There is an issue in CPython when using `bytes.decode("unicode_escape", error="ignore|replace")`. If you are not using the "unicode_escape" encoding or an error handler your usage is not affected. To work-around this issue you may stop using the error= handle…
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Low 2.3
Default mimetype known files writeable on Windows
There is a defect in the CPython standard library module “mimetypes” where on Windows the default list of known file locations are writable meaning other users can create invalid files to cause MemoryError to be raised on Python runtime startup or have file e…
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Medium 6.3
URL parser allowed square brackets in domain names
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…
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High 8.7
Unbounded memory buffering in SelectorSocketTransport.writelines()
Starting in Python 3.12.0, the asyncio._SelectorSocketTransport.writelines() method would not "pause" writing and signal to the Protocol to drain the buffer to the wire once the write buffer reached the "high-water mark". Because of this, Protocols would not …
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Medium 5.3
Virtual environment (venv) activation scripts don't quote paths
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/…
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High 7.5
Regular-expression DoS when parsing TarFile headers
There is a MEDIUM severity vulnerability affecting CPython. Regular expressions that allowed excessive backtracking during tarfile.TarFile header parsing are vulnerable to ReDoS via specifically-crafted tar archives.