SOC status:Duty analyst on shift

UK Cyber Defence
VulnerabilityAnalyzed

CVE-2026-3787

A weakness has been identified in UltraVNC 1.6.4.0 on Windows.

MEDIUM 6.4EPSS 0.17%

Does this matter?

Lower severity and a low EPSS score (0.17%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 4.0
6.4 MEDIUMCVSS: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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS
0.17% probability · 6th percentile
CISA KEV
Not listed
Weakness
CWE-426, CWE-427
Affected
uvnc/ultravnc
Source
cna@vuldb.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.