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Fencer Vulns
medium 5.3

CVE-2021-21419 json

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

published 2021-05-07 5 y ago modified 2026-07-08 4 mo ago also GHSA-9p9m-jm8w-94p2 , PYSEC-2021-12 , EUVD-2021-0072

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.8%
EPSS 1.8% chance of exploitation in 30 days, percentile 78%
public exploits
0
none known

Summary

Eventlet is a concurrent networking library for Python. A websocket peer may exhaust memory on Eventlet side by sending very large websocket frames. Malicious peer may exhaust memory on Eventlet side by sending highly compressed data frame. A patch in version 0.31.0 restricts websocket frame to reasonable limits. As a workaround, restricting memory usage via OS limits would help against overall machine exhaustion, but there is no workaround to protect Eventlet process.

Patch / fix

  • pypi eventlet 0.31.0
  • eventlet eventlet 0.31.0
  • python-eventlet Debian 14, Debian 13, Debian 12 0.26.1-7

debian advisories DEBIAN-CVE-2021-21419

  • python-eventlet Ubuntu 20.04 LTS 0.25.1-2ubuntu1.1

ubuntu advisories UBUNTU-CVE-2021-21419

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-eventlet openstack 16.1 0.25.2-5.el8ost.1
  • python3-eventlet openstack 16.1 0.25.2-5.el8ost.1
  • runc openshift 4.8 1.0.0-98.rhaos4.8.gitcd80260.el7
  • runc openshift 4.8 1.0.0-98.rhaos4.8.gitcd80260.el8
  • cri-o openshift 4.8 1.21.2-5.rhaos4.8.gitb27d974.el7
  • cri-o openshift 4.8 1.21.2-5.rhaos4.8.gitb27d974.el8
  • butane openshift 4.8 0.12.1-1.rhaos4.8.el8
  • ostree openshift 4.8 2020.7-5.el8_4

red hat advisories RHSA-2021:5071RHSA-2021:2437

  • kibana OpenStack Cloud Crowbar 9, OpenStack Cloud 9 4.6.6-4.12.1
  • influxdb OpenStack Cloud Crowbar 9, OpenStack Cloud 9 1.3.8-4.6.1
  • rubygem-puma OpenStack Cloud Crowbar 9 2.16.0-4.15.1
  • ardana-ansible OpenStack Cloud 9 9.0+git.1628097238.f6cbb0e-3.29.1
  • ardana-monasca OpenStack Cloud 9 9.0+git.1627995376.30bdf85-3.25.1
  • openstack-nova OpenStack Cloud Crowbar 9, OpenStack Cloud 9 18.3.1~dev91-3.40.1
  • python-eventlet OpenStack Cloud Crowbar 9, OpenStack Cloud 9 0.20.0-8.3.1
  • openstack-cinder OpenStack Cloud Crowbar 9, OpenStack Cloud 9 13.0.10~dev23-3.31.2

suse advisories SUSE-SU-2021:3729-1SUSE-SU-2021:2554-1

  • python-eventlet Arch Linux 0.31.0-1

arch linux advisories AVG-1928

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-21419 updated cvss 5.3

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

  • Red Hat OpenStack Platform 10 (Newton) python-eventlet
    affected: no fix planned “Out of support scope”
  • Red Hat OpenStack Platform 13 (Queens) python-eventlet Red Hat Storage 3 python-eventlet
    affected: no fix planned “Will not fix”
  • Red Hat OpenShift Container Platform 4.8 python-eventlet 0.25.2-4.el8, python3-eventlet 0.25.2-4.el8
    fixed: vendor fix RHSA-2021:2437
  • Red Hat OpenStack Platform 16.1 python-eventlet 0.25.2-5.el8ost.1, python3-eventlet 0.25.2-5.el8ost.1
    fixed: vendor fix RHSA-2021:5071
  • Red Hat OpenShift Container Platform 4.8 podman 3.0.1-6.el8, haproxy 2.2.13-1.el7, haproxy 2.2.13-1.el8, ostree 2020.7-5.el8_4, cri-tools 1.21.0-2.el7, cri-tools 1.21.0-2.el8, +132 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.79% chance of exploitation in the next 30 days, higher than 78% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
pypi eventlet
>=0.10, <0.31.0
>=0.10.0, <0.31.0
0.31.0

Affected products

  • eventlet eventlet

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.