CVE-2026-7831: falha de alta gravidade em uvnc UltraVNC
UltraVNC viewer off-by-one stack overflow in ServerInit desktop name parsing
Publicada em · Atualizada em
Aviso por e-mail quando ela entrar no KEV, ganhar PoC pública ou subir de nota.
21Vexday Risk Score
Sem sinal de exploração. Nenhum artefato público de exploração conhecido até agora.
ssvc Trackcvss 7.5epss 0.7%
UltraVNC viewer through 1.8.2.2 contains an off-by-one stack buffer overflow in the RFB ServerInit message handler. In vncviewer/ClientConnection.cpp, when the server-supplied nameLength equals exactly 2024 the code declares a 2024-byte stack buffer _dn[2024] and calls ReadString(_dn, 2024). ReadString writes the NUL terminator at buf[length], i.e., _dn[2024], one byte past the end of the stack buffer. A malicious VNC server can trigger this condition by advertising a desktop name of length 2024 in its ServerInit message. On release builds without stack canaries the single-byte NUL overwrite adjacent stack data. On builds with /GS stack protection the canary is corrupted and the process terminates, resulting in denial of service. User interaction (connecting the viewer to the malicious server) is required.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H
Produtos afetados
uvnc · UltraVNCCVEs relacionadas — uvnc UltraVNC
No mesmo produto, das mais perigosas para as menos.
CVE-2026-7840CRITICALUltraVNC repeater HTTP server global buffer overflow via long URI (pre-auth RCE)EPSS 2.6%CVE-2026-7838HIGHUltraVNC viewer heap buffer overflow via integer overflow in RFB connection-failure reason lengthEPSS 1.9%CVE-2026-7828MEDIUMUltraVNC repeater integer overflow in win_log malloc leading to heap overflowEPSS 1.4%CVE-2026-7829HIGHUltraVNC repeater authenticated out-of-bounds write in rule parser via oversized tokenEPSS 0.9%CVE-2026-7839CRITICALUltraVNC repeater ships hardcoded default admin password allowing unauthenticated admin accessEPSS 0.7%CVE-2026-44042LOWUltraVNC repeater wi_uudecode off-by-one in base64 decode boundary checkEPSS 0.5%