Medium severity · published May 7, 2021
CVE-2021-21419
Eventlet is a concurrent networking library for Python
5.3
CVSS
1.8%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.8% · higher than 78% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
EV
Eventlet · Eventlet
0.10 before 0.31.0 · source: NVD
FE
Fedora · Fedoraproject
33; 34 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-21419
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-21419
Third Party Advisory
https://github.com/eventlet/eventlet/security/advisories/GHSA-9p9m-jm8w-94p2
lists.fedoraproject.org
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2WJFSBPLCNSZNHYQC4QDRDFRTEZRMD2L/
lists.fedoraproject.org
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R5JZP4LZOSP7CUAM3GIRW6PIAWKH5VGB/
More from Eventlet
9.1
CVE-2025-58068
Eventlet is a concurrent networking library for Python
7.0
CVE-2023-29483
eventlet before 0.35.2, as used in dnspython before 2.6.0, allows remote attackers to interfere with DNS name resolution by quickly sending an invalid packet from the expected IP…