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CVE-2021-41380

22
FAUCET Score

CVE-2021-41380 describes a denial-of-service vulnerability in RealVNC Viewer 6.21.406, where a remote VNC server can crash the application using crafted RFB protocol data. This medium-severity vulnerability (CVSS 6.5) requires user interaction, specifically social engineering to connect to a malicious server, leading to an application hang rather than data compromise. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this issue.

Impacted Technologies

VendorProductVersion(s)CPE
6.21.406CPE matchmatch criteria
cpe:2.3:a:realvnc:vnc_viewer:6.21.406:*:*:*:*:*:*:*

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
0.96%
Probability of exploitation in next 30 days
EPSS Percentile
57.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0096 is in the 70th 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

Remediation records are not available for this CVE.

References

gist.github.com / totaam/a90f2bb40f5b693ccec0ae903d021b03
ExploitThird Party Advisory