A vulnerability, which was classified as critical, was found in UltraVNC up to 1.2.2.3 (Connectivity Software). This affects the function ClientConnection::Copybuffer of the component VNC Client Mode. The manipulation with an unknown input leads to a out-of-bounds vulnerability. CWE is classifying the issue as CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The bug was discovered 03/01/2019. The weakness was released 03/08/2019 by Pavel Cheremushkin with Kaspersky Lab ICS CERT as KLCERT-19-013: UltraVNC Access of Memory Location After End of Buffer as confirmed advisory (Website). It is possible to read the advisory at ics-cert.kaspersky.com. The original advisory by Kaspersky has a very bad quality and consists of contradicting statements (e.g. summary and CVSS vectors). This vulnerability is uniquely identified as CVE-2019-8266 since 02/12/2019. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The advisory points out:

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 code execution. This attack appear to be exploitable via network connectivity. User interaction is required to trigger these vulnerabilities. These vulnerabilities have been fixed in revision 1208.

The vulnerability was handled as a non-public zero-day exploit for at least 7 days. During that time the estimated underground price was around $5k-$25k. The advisory illustrates:

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code.

Upgrading to version 1.2.2.4 eliminates this vulnerability. Applying the patch Revision 1208 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version. A possible mitigation has been published 6 days after the disclosure of the vulnerability.

Further details are available at us-cert.gov. Entries connected to this vulnerability are available at 131509, 131510, 131512 and 131513.

Productinfo

Type

• Connectivity Software

Name

• UltraVNC

Version

• 1.0.4
• 1.0.5
• 1.0.5.1
• 1.0.8.2
• 1.0.9.5
• 1.0.9.6
• 1.0.9.6.2
• 1.1.4
• 1.1.5
• 1.1.8.0
• 1.1.8.3
• 1.1.8.4
• 1.1.8.5
• 1.1.8.6
• 1.1.8.9
• 1.1.9.0
• 1.1.9.1
• 1.1.9.3
• 1.1.9.6
• 1.2.0.1
• 1.2.0.3
• 1.2.0.4
• 1.2.0.5
• 1.2.0.6
• 1.2.0.7
• 1.2.0.9
• 1.2.1.1
• 1.2.1.2
• 1.2.1.6
• 1.2.1.7
• 1.2.2.1
• 1.2.2.2
• 1.2.2.3

License

• open-source

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CPE 2.2info

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