CVE-2021-41380

6.5 MEDIUM

RealVNC Viewer 6.21.406 allows remote VNC servers to cause a denial of service (application crash) via crafted RFB protocol data

Published: 2021-09-17 · Last updated: 2026-06-17

Severity and scoring

CVSS: 6.5 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
CWE: CWE-20

Affected products

Vendor	Product
realvnc	vnc_viewer

Description

RealVNC Viewer 6.21.406 allows remote VNC servers to cause a denial of service (application crash) via crafted RFB protocol data. NOTE: It is asserted that this issue requires social engineering a user into connecting to a fake VNC Server. The VNC Viewer application they are using will then hang, until terminated, but no memory leak occurs - the resources are freed once the hung process is terminated and the resource usage is constant during the hang. Only the process that is connected to the fake Server is affected. This is an application bug, not a security issue

Source: NVD

References

[NVD]https://nvd.nist.gov/vuln/detail/CVE-2021-41380
[Exploit reference]https://gist.github.com/totaam/a90f2bb40f5b693ccec0ae903d021b03
[Exploit reference]https://gist.github.com/totaam/a90f2bb40f5b693ccec0ae903d021b03

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