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CVE-2021-21419

20
FAUCET Score

CVE-2021-21419 describes a denial-of-service vulnerability in Eventlet, a Python concurrent networking library, and its associated Fedora packages. A malicious actor can exhaust memory on the Eventlet side by sending excessively large or highly compressed WebSocket frames. This vulnerability has a CVSS score of 5.3 (Medium), indicating it can be exploited over the network with low complexity and no user interaction, leading to a loss of availability. There is no evidence of active exploitation, public exploit code, or significant community discussion, and it is not listed on the CISA KEV catalog.

Impacted Technologies

VendorProductVersion(s)CPE
>= 0.10, < 0.31.0CPE matchmatch criteria
cpe:2.3:a:eventlet:eventlet:*:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
LOW
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.81%
Probability of exploitation in next 30 days
EPSS Percentile
76.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0181 is in the 63rd percentile among its peer group of 23,723 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (6)

elasticpatch availablevia llm_extracted
Fixed in: ['8.1.13', '8.2.10', '9.0.4', '9.0.2209.3']
pippatch availablevia ghsa
Product: eventletFixed in: 0.31.0
redhatpatch availablevia redhat_api
Product: Red Hat OpenShift Container Platform 4.8Fixed in: python-eventlet-0:0.25.2-4.el8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat OpenStack Platform 16.1Fixed in: python-eventlet-0:0.25.2-5.el8ost.1
View patch
redhatend of lifevia redhat_api
Product: Red Hat OpenStack Platform 13 (Queens)Fixed in: python-eventlet
redhatend of lifevia redhat_api
Product: Red Hat Storage 3Fixed in: python-eventlet

Vendor Advisories (3)

elasticllm-elastic-1862d04bb8fb6af4HIGH

February Third Party Package Updates in Splunk Enterprise

Feb 14, 2023
pipGHSA-9p9m-jm8w-94p2medium

Improper Handling of Highly Compressed Data (Data Amplification) and Memory Allocation with Excessive Size Value in eventlet

May 7, 2021
redhatCVE-2021-21419Moderate

python-eventlet: improper handling of highly compressed data and memory allocation with excessive size allows DoS

May 6, 2021

References

github.com / eventlet/eventlet/security/advisories/GHSA-9p9m-jm8w-94p2
Third Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/2WJFSBPLCNSZNHYQC4QDRDFRTEZRMD2L
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/R5JZP4LZOSP7CUAM3GIRW6PIAWKH5VGB