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Description

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.

PUBLISHED Reserved 2026-03-22 | Published 2026-03-22 | Updated 2026-03-24 | Assigner VulnCheck




HIGH: 7.1CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
MEDIUM: 6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Problem types

Out-of-bounds Write

Product status

1.2.2.4
affected

Credits

Victor Mondragón finder

References

www.exploit-db.com/exploits/46702 (ExploitDB-46702) exploit

www.uvnc.com/ (Official Product Homepage) product

www.uvnc.com/...ads/ultravnc/126-download-ultravnc-1224.html (Product Reference) product

www.vulncheck.com/...r-denial-of-service-via-buffer-overflow (VulnCheck Advisory: UltraVNC Viewer 1.2.2.4 Denial of Service via Buffer Overflow) third-party-advisory

cve.org (CVE-2019-25600)

nvd.nist.gov (CVE-2019-25600)

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