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CVE-2021-28166

21
FAUCET Score

CVE-2021-28166 affects Eclipse Mosquitto versions 2.0.0 to 2.0.9, where a NULL pointer dereference can be triggered by an authenticated MQTT v5 client sending a crafted CONNACK message to the broker. This vulnerability has a CVSS score of 6.5 (Medium), indicating it can be exploited remotely with low complexity by an authenticated attacker, leading to high availability impact. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
<= 2.0.9CPE match
cpe:2.3:a:eclipse:mosquitto:*:*:*:*:*:*:*:*
>= 2.0.0, <= 2.0.9CPE matchmatch criteria
cpe:2.3:a:eclipse:mosquitto:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
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
0.97%
Probability of exploitation in next 30 days
EPSS Percentile
58.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0097 is in the 71st percentile among its peer group of 21,974 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 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

bugs.eclipse.org / bugs/show_bug.cgi
Issue TrackingPatchVendor Advisory