CVE-2026-44040: uvnc UltraVNC

UltraVNC vncauth.c uses time-seeded libc rand() to generate VNC authentication challenge bytes

CVSS 4.8 MediumEPSS 0.0040 · 34th percentile

Published by the CVE Program (CNA: securin) at 1 Jul 2026, 03:33 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
uvnc	UltraVNC	affected 1.8.2.2 and earlier custom Other versions: unaffected

Identifiers

CVE-2026-44040

CNA

securin

Weakness (CWE)

CWE-338

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
4.8	Medium	3.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N	CNA (securin)

CISA KEV Not listed.
EPSS 0.0040, the 34th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 1 Jul 2026. New records show when each source confirmed them.

Sources

References from the CNA

uvnc.com/ vendor-advisory
github.com/ultravnc/UltraVNC product
www.securin.io/zero-days/cve-2026-44040-libc-rand-weak-rng-vnc-auth-challenge-ultravnc

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.