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UltravncApplication · Uvnc

CVE-2019-8261

CRITICAL · 9.8 CVSS v3.0 Published 2019-03-05
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 1199 has a out-of-bounds read vulnerability in VNC code inside client CoRRE decoder, caused by multiplication overflow. This attack appears to be exploitable via network connectivity. This vulnerability has been fixed in revision 1200.

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 1199 contains an out-of-bounds read vulnerability in the VNC client's CoRRE decoder caused by a multiplication overflow. An integer overflow during size calculations results in insufficient buffer allocation, leading to memory read operations beyond allocated boundaries. The flaw is exploitable remotely via network connectivity.

MitigationUpgrade UltraVNC to revision 1200 or later to patch the vulnerability. If immediate upgrade is not possible, restrict network access to VNC ports and monitor for anomalous connections.

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. Identify UltraVNC installation and version
    Check the installed version of UltraVNC by reviewing the executable properties. Common installation paths: C:\Program Files\UltraVNC\vncviewer.exe or C:\Program Files (x86)\UltraVNC\vncviewer.exe. Right-click the executable, select Properties, and examine the 'File version' or 'Product version' field. Alternatively, run 'wmic product where "name like '%UltraVNC%'" get version,name' in Command Prompt.
    Affected if The installed version is earlier than 1.2.2.3, or the file version shows revision 1199 or earlier (typically shown as x.x.x.x where the first components may indicate the revision).
  2. Confirm the vulnerable component is present
    Verify that the vncviewer.exe file exists in the expected UltraVNC installation directory. The vulnerability exists in the CoRRE decoder component of the VNC client, which is included in standard UltraVNC viewer installations.
    Affected if The vncviewer.exe file exists and its version matches the affected range (< 1.2.2.3).
  3. Check for active VNC client listening ports
    Open Command Prompt and run 'netstat -an | findstr "5900"' to check if any VNC client process is listening on typical VNC ports (5900 is the primary display port). Also run 'netstat -ano | findstr "LISTENING"' and look for entries associated with vncviewer.exe in the process list.
    Affected if The UltraVNC viewer is actively running and listening on network ports, indicating the client component is in use and potentially exposed to remote connections.
  4. Assess network exposure to VNC services
    Review firewall rules and network configuration. Run 'netsh advfirewall firewall show rule name=all' or check Windows Firewall inbound rules to determine if port 5900 (and nearby ports 5901-5910) are allowed through the firewall. Also check for any port forwarding rules on routers/firewalls directing traffic to the affected machine.
    Affected if Inbound connections to VNC ports (5900 range) are permitted by the firewall or router, allowing remote attackers to trigger the vulnerability through the CoRRE decoder.

A user is affected if UltraVNC viewer version 1.2.2.3 or earlier (revision 1199 or earlier) is installed and the system is exposed to incoming VNC connections on ports 5900-5910.

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 to revision 1200 or later to patch the vulnerability. If immediate upgrade is not possible, restrict network access to VNC ports and monitor for anomalous connections.

Recommended fix High confidence

UltraVNC 1.2.2.3 or later (revision 1200 and above)

  1. 1. Download UltraVNC version 1.2.2.3 or later from the official UltraVNC website (www.uvnc.com)
  2. 2. Uninstall the current vulnerable version of UltraVNC
  3. 3. Install the downloaded version 1.2.2.3 or later
  4. 4. Verify the installed version is 1.2.2.3 or higher by checking Help > About UltraVNC

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

Fix this in Ultravnc Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
6.0 hours of engineering $1,060
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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-2019-8261 in production — separate from our analysis above.

No notes yet

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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