UltraVNC Viewer VNC client RFB ReadUltraRect Heap Overflow Vulnerability


A vulnerability exists within UltraVNC’s “vncviewer.exe” client. Specifically a heap overflow can be triggered in the “ClientConnection::ReadUltraRect” function upon decompression of malicious formatted data returned from a nefarious server. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of the UltraVNC Viewer process.

Vulnerability Identifiers

  • Exodus Intelligence: EIP-930b0ea5

Vulnerability Metrics

  • CVSSv2 Score: 5.8

Vendor References

Discovery Credit

  • Exodus Intelligence

Disclosure Timeline

  • Disclosed to affected vendor: December 8th, 2021
  • Disclosed to public: December 16th, 2021

Further Information

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