Cyber Resilience

CVE-2021-3737

HighPublic PoCDDoS

Published: 04 March 2022

Published
04 March 2022
Modified
17 December 2025
KEV Added
Patch
CVSS Score v3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0012 30.4th percentile
Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-3737 is a high-severity Infinite Loop (CWE-835) vulnerability in Canonical Ubuntu Linux. Its CVSS base score is 7.5 (High).

Operationally, ranked at the 30.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

EU & UK References

Vulnerability details

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.…

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The highest threat from this vulnerability is to system availability.

CWE(s)

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

python
python
3.6.0 — 3.6.14 · 3.7.0 — 3.7.11 · 3.8.0 — 3.8.11
redhat
codeready linux builder
8.0
redhat
codeready linux builder for ibm z systems
8.0
redhat
codeready linux builder for power little endian
8.0
redhat
enterprise linux
6.0, 7.0, 8.0
redhat
enterprise linux for ibm z systems
8.0
redhat
enterprise linux for power little endian
8.0
fedoraproject
fedora
33, 34
canonical
ubuntu linux
14.04, 16.04, 18.04, 20.04, 21.04
netapp
hci
all versions
+7 more product configuration(s) — see NVD for full list

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-400 CWE-835

Alternate site allows resumption of operations if resource exhaustion at the primary site is exploited to cause unavailability.

addresses: CWE-400 CWE-835

Directly limits uncontrolled resource consumption that leads to denial-of-service.

addresses: CWE-400

Limiting concurrent sessions directly prevents uncontrolled resource consumption by capping the number of active sessions per user or account.

addresses: CWE-400

Analysis identifies uncontrolled resource consumption indicative of denial-of-service or abuse attempts.

addresses: CWE-400

Contingency plan testing includes resource exhaustion scenarios to verify recovery, making it harder for attackers to sustain exploits that cause uncontrolled consumption.

addresses: CWE-400

Updated contingency plans include current procedures to detect, contain, and recover from resource exhaustion, limiting an attacker's ability to sustain impact from uncontrolled consumption.

addresses: CWE-400

Alternate telecommunications services enable resumption of essential functions when primary services become unavailable due to uncontrolled resource consumption.

addresses: CWE-400

The team can analyze and respond to resource exhaustion incidents, reducing the impact of attacks that exploit uncontrolled consumption weaknesses.

References