What is CVE-2026-7838?

CVE-2026-7838 is a high-severity vulnerability in Uvnc Ultravnc, classified under Integer Overflow or Wraparound. CVSS score: 8.8/10. Published 2026-07-01.

How severe is CVE-2026-7838?

High severity. CVSS v3 base score is 8.8 out of 10.

Buffer overflow in Uvnc Ultravnc

CVE-2026-7838

UltraVNC viewer through 1.8.2.2 contains an integer overflow leading to a heap buffer overflow in the RFB protocol failure-response parsing path. In vncviewer/ClientConnection.cpp, the 4-byte network-supplied reasonLen field (type CARD32)…

Vulnerability class: Integer Overflow

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

Affected products

Uvnc Ultravnc — versions 0

Weakness classification (CWE)

CWE-190 — Integer Overflow or Wraparound
CWE-787 — Out-of-bounds Write

References

33c584b5-0579-4c06-b2a0-8d8329fcab9c (vendor-advisory)
33c584b5-0579-4c06-b2a0-8d8329fcab9c (product)

Frequently asked questions

What is CVE-2026-7838?: CVE-2026-7838 is a high-severity vulnerability in Uvnc Ultravnc, classified under Integer Overflow or Wraparound. CVSS score: 8.8/10. Published 2026-07-01.
How severe is CVE-2026-7838?: High severity. CVSS v3 base score is 8.8 out of 10.