CVE-2020-37133Public exploit

Application crash via unbounded Repeater Host input

Published Feb 5, 2026 · Updated Feb 5, 2026

Stack-based buffer overflow in UltraVNC Launcher 1.2.4.0 allows local users to crash the application through the Repeater Host field. The Repeater Host property accepts a 300-character string without adequate length validation, overflowing a stack buffer when the Properties dialog is confirmed. Exploitation requires local interactive access and an active user to paste the crafted value and click OK; the demonstrated consequence is a launcher crash.

CVSS severity6.7
Medium
EPSS probability0.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in UltraVNC Launcher 1.2.4.0 allows local users to crash the application through the Repeater Host field. The Repeater Host property accepts a 300-character string without adequate length validation, overflowing a stack buffer when the Properties dialog is confirmed. Exploitation requires local interactive access and an active user to paste the crafted value and click OK; the demonstrated consequence is a launcher crash.

The record

CVE
CVE-2020-37133
Published
Feb 5, 2026
Updated
Feb 5, 2026
Vendor
UltraVNC Team
Product
UltraVNC Launcher
Classifications
CWE-121, T1499
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.2.4.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

UltraVNC Team · UltraVNC Launcherversion=1.2.4.0

Published CVSS scores

6.7VulnCheckCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
7.5VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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