UltraVNC Viewer 1.2.4.0 contains a denial of service vulnerability that allows attackers to crash the application by manipulating VNC Server input. Attackers can generate a malformed 256-byte payload and paste it into the VNC Server connection dialog to trigger an application crash.

Attack Vector Local

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction Active

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact Low

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Exploitation poc

Automatable yes

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
UltraVNC Team UltraVNC Viewer affected
Version Status Constraints
1.2.4.0 affected —

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Project Subscriptions

No data.

Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://www.exploit-db.com/exploits/48291 cve-icon cve-icon
https://www.uvnc.com/ cve-icon cve-icon
https://www.vulncheck.com/advisories/ultravnc-viewer-vncserver-denial-of-service cve-icon cve-icon
History

Thu, 05 Feb 2026 19:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Thu, 05 Feb 2026 16:30:00 +0000

Type Values Removed Values Added
Description UltraVNC Viewer 1.2.4.0 contains a denial of service vulnerability that allows attackers to crash the application by manipulating VNC Server input. Attackers can generate a malformed 256-byte payload and paste it into the VNC Server connection dialog to trigger an application crash.
Title UltraVNC Viewer 1.2.4.0 - 'VNCServer' Denial of Service
Weaknesses CWE-770
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 4.6, 'vector': 'CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-02-05T18:43:12.397Z

Reserved: 2026-02-03T16:27:45.306Z

Link: CVE-2020-37134

cve-icon Vulnrichment

Updated: 2026-02-05T18:43:09.456Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-02-05T17:16:08.690

Modified: 2026-02-05T20:47:37.777

Link: CVE-2020-37134

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses