CVE-2021-3737
HIGHEPSS 96th pctlDescription
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.
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:N/I:N/A:H
Exploit Intelligence
Very high risk: more likely to be exploited than 96% of all known CVEs.
References
Related Vulnerabilities
Other CWE-835 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2020-13935 | High | 7.5 | 87% | - | Fix |
| CVE-2020-36227 | High | 7.5 | 78% | - | Fix |
| CVE-2024-20353 | High | 8.6 | 71% | KEV | - |
| CVE-2022-0778 | High | 7.5 | 71% | - | Fix |
| CVE-2019-14241 | High | 7.5 | 70% | - | - |
| CVE-2017-16944 | High | 7.5 | 63% | - | Fix |
Common questions
How do I fix CVE-2021-3737?
Published advisories record a fix for 29 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-2021-3737 being actively exploited?
Not that we know of. CVE-2021-3737 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 11.6% is the estimated probability that it will be exploited in the next 30 days. That is higher than 96% of all scored CVEs.
How severe is CVE-2021-3737?
CVE-2021-3737 has a CVSS v3 base score of 7.5, rated high. 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-2021-3737 affect?
Published advisories record a fix for pypy3 (Debian), libpython3.6-stdlib (Ubuntu), libpython3.7-stdlib (Ubuntu), libpython3.8-stdlib (Ubuntu), and 25 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2021-3737
Markdown
[](https://tridentstack.com/cve/CVE-2021-3737)HTML
<a href="https://tridentstack.com/cve/CVE-2021-3737"><img src="https://tridentstack.com/cve/badge/CVE-2021-3737.svg" alt="CVE-2021-3737"></a>Find and fix vulnerabilities across your fleet
TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.
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 2025-12-17.