CVE-2021-3177
CRITICALEPSS 98th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
Very high risk: more likely to be exploited than 98% of all known CVEs.
References
- lists.apache.org
- lists.debian.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
Related Vulnerabilities
Other CWE-120 (Classic Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2014-0195 | Medium | 6.8 | 100% | - | Fix |
| CVE-2017-7269 | Critical | 9.8 | 100% | KEV | - |
| CVE-2019-11043 | High | 8.7 | 99% | KEV + Ransom | Fix |
| CVE-2011-4862 | High | 10.0 | 95% | - | Fix |
| CVE-2007-5659 | High | 7.8 | 94% | KEV | Fix |
| CVE-2022-3786 | High | 7.5 | 92% | - | Fix |
Common questions
How do I fix CVE-2021-3177?
Published advisories record a fix for 21 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2021-3177 being actively exploited?
Not that we know of. CVE-2021-3177 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 23.3% is the estimated probability that it will be exploited in the next 30 days. That is higher than 98% of all scored CVEs.
How severe is CVE-2021-3177?
CVE-2021-3177 has a CVSS v3 base score of 9.8, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-3177 affect?
Published advisories record a fix for python2.7 (Debian), python2.7 (Ubuntu), python2.7-minimal (Ubuntu), python3.10 (Ubuntu), and 17 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-12-18.