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CVE-2018-15361: Uvnc Ultravnc: Code execution

CVE-2018-15361 is rated critical with a CVSS v3.0 base score of 9.8 and affects Uvnc Ultravnc. Per its scoring, it can be exploited over the network, without authentication, without any user interaction. The scored impact on confidentiality, integrity and availability is the highest available.

Vulnerability description

UltraVNC revision 1198 has a buffer underflow vulnerability in VNC client code, which can potentially result in code execution. This attack appears to be exploitable via network connectivity. This vulnerability has been fixed in revision 1199.

Severity breakdown

CVSS v3.0 9.8: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

• Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
• Attack complexity: Low. No special conditions; the attack can be repeated reliably.
• Privileges required: None. No account or prior access is needed.
• User interaction: None. No action from any user is needed.
• Scope: Unchanged. Impact stays within the vulnerable component.
• Confidentiality impact: High. Total loss of confidentiality; sensitive data can be fully disclosed.
• Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
• Availability impact: High. Total loss of availability; the component can be shut down.

Underlying weakness

CWE-124: Buffer Underwrite

The product writes to a buffer using an index or pointer that references a memory location prior to the beginning of the buffer.

CWE-787: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

Affected products

• Uvnc Ultravnc: before 1.2.2.3

References

• https://ics-cert.kaspersky.com/advisories/klcert-advisories/2019/03/01/klcert-19-003-ultravnc-buffer-underwrite/
• https://cert-portal.siemens.com/productcert/pdf/ssa-927095.pdf
• https://www.us-cert.gov/ics/advisories/icsa-20-161-06