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CVE-2021-20234

22
FAUCET Score

CVE-2021-20234 describes an uncontrolled resource consumption (memory leak) vulnerability in the ZeroMQ client, specifically in versions prior to 4.3.3. This flaw, located in src/pipe.cpp, can lead to a denial of service by causing the client to crash if it connects to multiple malicious or compromised servers. Rated with a CVSS score of 6.5 (Medium), the vulnerability has a network attack vector and low attack complexity, requiring user interaction (UI:R) but no privileges. The primary impact is high availability (A:H), with no impact on confidentiality or integrity. Currently, there is no evidence of active exploitation, nor are there any public exploit codes available on platforms like Metasploit or ExploitDB. Community discussion and media coverage for this CVE are also minimal, indicating low public attention.

Impacted Technologies

VendorProductVersion(s)CPE
< 4.3.3CPE matchmatch criteria
cpe:2.3:a:zeromq:libzmq:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.07%
Probability of exploitation in next 30 days
EPSS Percentile
61.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0107 is in the 74th percentile among its peer group of 26,236 CVEs.

Social Chatter

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

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
redhatpatch availablevia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2021-20234Low

zeromq: Memory leak in client induced by malicious server without CURVE/ZAP

Sep 7, 2020

References

bugzilla.redhat.com / show_bug.cgi
Issue TrackingPatchThird Party Advisory
github.com / zeromq/libzmq/security/advisories/GHSA-wfr2-29gj-5w87
ExploitPatchThird Party Advisory