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Vulnerabilities

Vulnerability · 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…

Published Jan 19, 2021 · catalog updated Oct 14, 2026 · the affected product

Check this week

CVE-2021-3177 is not in CISA KEV. FIRST estimates a 24.22% chance of exploitation in the next 30 days. Check whether you run the affected product.

Gaps on this record

  • No plain product name is stored. The page cannot tell you which product to check.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Critical9.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
24.22%
Remediation
Advisory link
Affected products
cpe debian/debian linux · cpe fedoraproject/fedora · cpe netapp/active iq unified manager · cpe oracle/communications cloud native core network function cloud native environment · cpe python/python

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe debian/debian linux9.0
  • cpe fedoraproject/fedora32
  • cpe fedoraproject/fedora33
  • cpe netapp/active iq unified managerversion unspecified
  • cpe oracle/communications cloud native core network function cloud native environment22.2.0
  • cpe python/pythonversion unspecified

How to fix CVE-2021-3177

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-3177 is not in CISA KEV. FIRST estimates a 24.22% chance of exploitation in the next 30 days. Check whether you run the affected product.

Which versions are affected?

Compare what you have installed with debian/debian linux 9.0; oracle/communications cloud native core network function cloud native environment 22.2.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-120: Classic Buffer Overflow. EPSS 24.22%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Jan 19, 2021 · NIST NVD

    Detected

    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.

  2. Oct 14, 2026 · NIST NVD

    Updated

    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.

Sources

  • CVE.orgVulnerability recordCVE-2021-3177

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-3177

    30-day exploitation probability 24.22%

    first.org
  • NIST NVDVulnerability recordCVE-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 occu

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 24, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.