CVE-2021-3177
CVSS v3
9.8
CRITICAL
EPSS Score
23.3 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
Description
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.
Technical details
- Published
- 2021-01-19
Frequently asked questions
What is CVE-2021-3177?
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.
Is CVE-2021-3177 actively exploited?
Active exploitation of CVE-2021-3177 has not been confirmed. Its EPSS score was 23.3% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2021-3177?
CVE-2021-3177 has a CVSS v3 base score of 9.8 (CRITICAL severity).
Is CVE-2021-3177 affecting your environment?
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