CVE-2021-3177
CriticalCVSS 9.8Exploitation Probability (EPSS)
Very high risk98th percentile - higher than 98% of all known CVEs
Summary
Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain Python applications that accept floating-point numbers as untrusted input, as demonstrated by a 1e300 argument to c_double.from_param. This occurs because sprintf is used unsafely.
Risk Assessment
An attacker could remotely execute code in an application using the vulnerable Python version, potentially leading to system compromise or data breach.
Recommendation
Upgrade Python to version 3.9.2 or later, which includes a fix for this vulnerability.
Other vulnerabilities in Python
See all- CVE-2026-85864High
Improper privilege management in Python allows an authorized attacker to elevate privileges locally.
- CVE-2013-7338High
Python versions before 3.3.4 RC1 allow remote attackers to cause a denial of service via a file size value larger than the size of the zip file in functions related to reading and extracting zip files.
- CVE-2026-1299Medium
The email module in Python, specifically the BytesGenerator class, improperly quotes newlines in email headers during serialization, allowing header injection. This only affects usage of LiteralHeader that does not respect email folding.
- CVE-2023-24329High
A vulnerability in the urllib.parse component of Python before version 3.11.4 allows attackers to bypass blocklisting methods by supplying a URL that starts with blank characters.
- CVE-2023-27043Medium
The email module in Python through 3.11.3 incorrectly parses email addresses containing special characters. The wrong portion of an RFC2822 header is identified as the value of the addr-spec.
- CVE-2022-42919High
A vulnerability in Python 3.9.x before 3.9.16 and 3.10.x before 3.10.9 on Linux allows local privilege escalation in a non-default configuration. The multiprocessing library with the forkserver start method permits pickle deserialization from any user on the same local network of the machine.
- CVE-2022-0391High
A flaw was found in Python's urllib.parse module where the urlparse method does not sanitize input, allowing characters like ' ' and ' ' in the URL path. This can lead to CRLF injection attacks.
- CVE-2020-10735High
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.from_bytes(), and int() for binary bases 2, 4, 8, 16, and 32 are not affected). The highest threat from this vulnerability is to system availability.
- CVE-2021-3737High
A flaw in Python's HTTP client code, when improperly handling an HTTP response, may cause the client script to enter an infinite loop, consuming CPU time. The highest threat is to system availability.
- CVE-2021-29921Critical
In Python before 3.9.5, the ipaddress library mishandles leading zero characters in the octets of an IP address string. This (in some situations) allows attackers to bypass access control that is based on IP addresses.
Original NVD description (English source)
Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain Python applications that accept floating-point numbers as untrusted input, as demonstrated by a 1e300 argument to c_double.from_param. This occurs because sprintf is used unsafely.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

