dbcve.org
UltravncApplication · Uvnc

CVE-2019-8266

CRITICAL · 9.8 CVSS v3.0 Published 2019-03-08
Fix available
A fix is available. Upgrade to 1.2.2.3 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
UltraVNC revision 1207 has multiple out-of-bounds access vulnerabilities connected with improper usage of ClientConnection::Copybuffer function in VNC client code, which can potentially result in code execution. This attack appears to be exploitable via network connectivity. User interaction is required to trigger these vulnerabilities. These vulnerabilities have been fixed in revision 1208.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

UltraVNC revision 1207 contains multiple out-of-bounds access vulnerabilities in the ClientConnection::Copybuffer function within the VNC client code. These memory corruption flaws can be exploited via network connectivity to potentially achieve code execution, though user interaction is required to trigger them. The vulnerabilities were patched in revision 1208.

MitigationUpgrade UltraVNC from revision 1207 to revision 1208 or later. Verify all deployed UltraVNC client installations are updated, as the vulnerable client code executes when users connect to remote VNC servers.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
UltravncApplication
Affected:< 1.2.2.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if UltraVNC client is installed
    Look for UltraVNC installation on the system - typically in Program Files folder on Windows, or check installed programs list
    Affected if UltraVNC client software is present on the system
  2. Determine installed UltraVNC version
    Open UltraVNC and check Help > About, or look at the executable version properties (vncviewer.exe)
    Affected if Version shown is earlier than 1.2.2.3 or revision 1207
  3. Identify the specific revision number
    Within UltraVNC About dialog or version properties, check the revision/build number displayed
    Affected if Revision is 1207 or earlier (versions prior to the 1.2.2.3 release containing revision 1208 fix)
  4. Confirm client component presence
    Verify the vncviewer.exe client executable exists - this is the component containing the vulnerable ClientConnection::Copybuffer function
    Affected if VNC viewer client component is installed and available for use
  5. Assess remote connection usage
    Determine if users utilize the UltraVNC client to connect to remote VNC servers - the vulnerability requires user interaction via connecting to a remote server
    Affected if Users connect to remote VNC servers using the UltraVNC client viewer

If UltraVNC client version earlier than 1.2.2.3 (revision 1207 or prior) is installed and users connect to remote VNC servers, the environment is affected by this vulnerability.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.2.2.3 or later
Fixed in 1.2.2.3
Interim mitigation

Upgrade UltraVNC from revision 1207 to revision 1208 or later. Verify all deployed UltraVNC client installations are updated, as the vulnerable client code executes when users connect to remote VNC servers.

Recommended fix High confidence

UltraVNC version 1.2.2.3 (revision 1208)

  1. 1. Download the fixed version of UltraVNC (version 1.2.2.3 or later, which includes revision 1208) from the official UltraVNC website or a trusted source
  2. 2. Ensure all UltraVNC server and client instances are updated to prevent exploitation between mismatched versions
  3. 3. Before upgrading, backup any existing UltraVNC configuration files if desired
  4. 4. Close any running UltraVNC processes on the machine
  5. 5. Run the installer for the new version and follow the installation prompts
  6. 6. After installation, restart the UltraVNC service or application
  7. 7. Verify the installed version matches or exceeds 1.2.2.3

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ultravnc Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2019-8266 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data