An issue in the urllib.parse component of Python before 3.11.4 allows attackers to bypass blocklisting methods by supplying a URL that starts with blank characters.

A use-after-free exists in Python through 3.9 via heappushpop in heapq.

A vulnerability was discovered in Python. A quadratic algorithm exists when processing inputs to the IDNA (RFC 3490) decoder, such that a crafted unreasonably long name being presented to the decoder could lead to a CPU denial of service. Hostnames are often supplied by remote servers that could be controlled by a malicious actor, which could trigger excessive CPU consumption on the client attempting to make use of an attacker-supplied hostname.

Fixed bug : buffer overflow in hashupdate() on long parameter. (CVE-2022-37454)

In Python before 3.10.3 on Windows, local users can gain privileges because the search path is inadequately secured. The installer may allow a local attacker to add user-writable directories to the system search path. To exploit, an administrator must have installed Python for all users and enabled PATH entries. A non-administrative user can trigger a repair that incorrectly adds user-writable paths into PATH, enabling search-path hijacking of other users and system services. This affects Python (CPython) through 3.7.12, 3.8.x through 3.8.12, 3.9.x through 3.9.10, and 3.10.x through 3.10.2.

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 attacker to input a crafted URL, leading to injection attacks.

DISPUTED Python 3.x through 3.10 has an open redirection vulnerability in lib/http/server.py due to no protection against multiple (/) at the beginning of URI path which may leads to information disclosure. NOTE: this is disputed by a third party because the http.server.html documentation page states "Warning: http.server is not recommended for production. It only implements basic security checks."

Impact

Users who are using an HTTPS proxy to issue HTTPS requests and haven't configured their own SSLContext via proxyconfig. Only the default SSLContext is impacted.

Patches

urllib3 >=1.26.4 has the issue resolved. urllib3<1.26 is not impacted due to not supporting HTTPS requests via HTTPS proxies.

Workarounds

Upgrading is recommended as this is a minor release and not likely to break current usage.

Configuring an SSLContext with checkhostname=True and passing via proxyconfig instead of relying on the default SSLContext

For more information If you have any questions or comments about this advisory: Email us at sethmichaellarson@gmail.com

Python CPython could allow a remote attacker to bypass security restrictions, caused by a web cache poisoning flaw via urllib.parse.parseqsl and urllib.parse.parseqs. By sending a specially-crafted request parameter cloaking, an attacker could exploit this vulnerability to cause a difference in the interpretation of the request between the proxy and the server.

A flaw was found in Python, specifically in the FTP (File Transfer Protocol) client library in PASV (passive) mode. The issue is how the FTP client trusts the host from the PASV response by default. This flaw allows an attacker to set up a malicious FTP server that can trick FTP clients into connecting back to a given IP address and port. This vulnerability could lead to FTP client scanning ports, which otherwise would not have been possible.

Last updated 25 August 2025

A flaw was found in python. An improperly handled HTTP response in the HTTP client code of python may allow a remote attacker, who controls the HTTP server, to make the client script enter an infinite loop, consuming CPU time. The highest threat from this vulnerability is to system availability.

A flaw was found in Python 3's pydoc. This flaw allows a local or adjacent attacker who discovers or can convince another local or adjacent user to start a pydoc server to access the server and then use it to disclose sensitive information belonging to the other user that they would not normally have the ability to access. The highest threat from this vulnerability is to data confidentiality.

A flaw was found in python. A stack-based buffer overflow was discovered in the ctypes module provided within Python. Applications that use ctypes without carefully validating the input passed to it may be vulnerable to this flaw, which would allow an attacker to overflow a buffer on the stack and crash the application. The highest threat from this vulnerability is to system availability.

A flaw was found in Python. The built-in modules httplib and http.client (included in Python 2 and Python 3, respectively) do not properly validate CRLF sequences in the HTTP request method, potentially allowing manipulation to the request by injecting additional HTTP headers. The highest threat from this vulnerability is to confidentiality and integrity.

In Python 3.8.4, sys.path restrictions specified in a python38.pth file are ignored, allowing code to be loaded from arbitrary locations. The <executable-name>.pth file (e.g., the python.pth file) is not affected.

In Python 3.6 through 3.6.10, 3.7 through 3.7.8, 3.8 through 3.8.4rc1, and 3.9 through 3.9.0b4 on Windows, a Trojan horse python3.dll might be used in cases where CPython is embedded in a native application. This occurs because python3X.dll may use an invalid search path for python3.dll loading (after PySetPath has been used). NOTE: this issue CANNOT occur when using python.exe from a standard (non-embedded) Python installation on Windows.

A vulnerability was found in Lib/ipaddress.py in Python through 3.8.3 improperly computes hash values in the IPv4Interface and IPv6Interface classes, which might allow a remote attacker to cause a denial of service if an application is affected by the performance of a dictionary containing IPv4Interface or IPv6Interface objects, and this attacker can cause many dictionary entries to be created.

References: https://bugs.python.org/issue41004 https://github.com/python/cpython/pull/20956

Last updated 25 August 2025

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.

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 not affected). The highest threat from this vulnerability is to system availability.

A flaw was found in python. In Lib/tarfile.py an attacker is able to craft a TAR archive leading to an infinite loop when opened by tarfile.open, because procpax lacks header validation.

Last updated 25 August 2025

An issue was discovered in urllib2 in Python 2.x through 2.7.16 and urllib in Python 3.x through 3.7.2. CRLF injection is possible if the attacker controls a url parameter, as demonstrated by the first argument to urllib.request.urlopen with \r\n (specifically in the path component of a URL) followed by an HTTP header or a Redis command. This is similar to CVE-2019-9740 query string issue.

Reference: https://bugs.python.org/issue35906

An issue was discovered in urllib2 in Python 2.x through 2.7.16 and urllib in Python 3.x through 3.7.2. CRLF injection is possible if the attacker controls a url parameter, as demonstrated by the first argument to urllib.request.urlopen with \r\n followed by an HTTP header or a Redis command.

Reference: https://bugs.python.org/issue36276

A vulnerability was found in Python 2.7.x through 2.7.16 and 3.x through 3.7.2. An improper Handling of Unicode Encoding (with an incorrect netloc) during NFKC normalization could lead to an Information Disclosure (credentials, cookies, etc. that are cached against a given hostname) in the urllib.parse.urlsplit, urllib.parse.urlparse components. A specially crafted URL could be incorrectly parsed to locate cookies or authentication data and send that information to a different host than when parsed correctly.

References: https://bugs.python.org/issue36216 https://python-security.readthedocs.io/vuln/urlsplit-nfkc-normalization.html

Uptream Patch: https://github.com/python/cpython/pull/12201

Last updated 18 August 2025

A CRLF injection flaw was discovered in python in the way URLs are handled when doing an HTTP/HTTPS connection (e.g. through urlopen() or HTTPConnection). An attacker who can control the url parameter passed to urlopen method in the urllib/urllib2 modules can inject CRLF sequences and HTTP headers by abusing the "host" part of the URL.

An issue was discovered in Python through 2.7.16, 3.x through 3.5.7, 3.6.x through 3.6.9, and 3.7.x through 3.7.4. The email module wrongly parses email addresses that contain multiple @ characters. An application that uses the email module and implements some kind of checks on the From/To headers of a message could be tricked into accepting an email address that should be denied. An attack may be the same as in CVE-2019-11340; however, this CVE applies to Python more generally.

In libexpat before 2.2.8, crafted XML input could fool the parser into changing from DTD parsing to document parsing too early; a consecutive call to XMLGetCurrentLineNumber (or XMLGetCurrentColumnNumber) then resulted in a heap-based buffer over-read.