Buffer overflow in Uvnc Ultravnc Viewer
CVE-2019-25600
UltraVNC Viewer 1.2.2.4 contains a denial of service vulnerability that allows attackers to crash the application by supplying an oversized string to the VNC Server input field. Attackers can paste a malicious string containing 256 repeated characters into the VNC Server field and click Connect to trigger a buffer overflow that crashes the viewer.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.007 (50.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 50.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000
Affected products
- Uvnc Ultravnc Viewer — versions 1.2.2.4
Weakness classification (CWE)
References
- www.exploit-db.com/exploits/46702 (exploit)
- www.uvnc.com/ (product)
- www.uvnc.com/downloads/ultravnc/126-download-ultravnc-1224.html (product)
- www.vulncheck.com/advisories/ultravnc-viewer-denial-of-service-via-buffer-overf… (third-party-advisory)
Frequently asked questions
- What is CVE-2019-25600?
- CVE-2019-25600 is a medium-severity vulnerability in Uvnc Ultravnc Viewer, classified under Out-of-bounds Write. CVSS score: 6.5/10. Published 2026-03-22.
- How severe is CVE-2019-25600?
- Medium severity. CVSS v3 base score is 6.5 out of 10.