CVE-2026-7831Network attack vector

Viewer crash via off-by-one desktop-name write

Published Jul 1, 2026 · Updated Jul 1, 2026

Stack buffer overflow in the UltraVNC viewer through 1.8.2.2 allows remote attackers to crash the client via a malicious VNC server. When nameLength is 2024, ClientConnection.cpp passes a 2024-byte stack buffer to ReadString, which writes its terminator to _dn[2024]. The user must connect the viewer to the malicious server; the one-byte overwrite corrupts adjacent stack data or trips /GS protection and terminates the viewer.

CVSS severity7.6
High
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack buffer overflow in the UltraVNC viewer through 1.8.2.2 allows remote attackers to crash the client via a malicious VNC server. When nameLength is 2024, ClientConnection.cpp passes a 2024-byte stack buffer to ReadString, which writes its terminator to _dn[2024]. The user must connect the viewer to the malicious server; the one-byte overwrite corrupts adjacent stack data or trips /GS protection and terminates the viewer.

The record

CVE
CVE-2026-7831
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
UltraVNC Team
Product
UltraVNC
Classifications
CWE-787, CWE-193, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=1.8.2.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

UltraVNC Team · UltraVNCversion=0 <=1.8.2.2

Published CVSS scores

7.6securinCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-193Off-by-one Error
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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