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Vulnerabilities
Vulnerable Software

Vulnerability Details CVE-2026-7831

UltraVNC viewer through 1.8.2.2 contains an off-by-one stack buffer overflow in the RFB ServerInit message handler. In vncviewer/ClientConnection.cpp, when the server-supplied nameLength equals exactly 2024 the code declares a 2024-byte stack buffer _dn[2024] and calls ReadString(_dn, 2024). ReadString writes the NUL terminator at buf[length], i.e., _dn[2024], one byte past the end of the stack buffer. A malicious VNC server can trigger this condition by advertising a desktop name of length 2024 in its ServerInit message. On release builds without stack canaries the single-byte NUL overwrite adjacent stack data. On builds with /GS stack protection the canary is corrupted and the process terminates, resulting in denial of service. User interaction (connecting the viewer to the malicious server) is required.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.004
EPSS Ranking 33.5%
CVSS Severity
CVSS v3 Score 7.6
Products affected by CVE-2026-7831
  • Uvnc » Ultravnc » Version: 1.0.9.6.2
    cpe:2.3:a:uvnc:ultravnc:1.0.9.6.2
  • Uvnc » Ultravnc » Version: 1.1.8.9
    cpe:2.3:a:uvnc:ultravnc:1.1.8.9
  • Uvnc » Ultravnc » Version: 1.1.9.3
    cpe:2.3:a:uvnc:ultravnc:1.1.9.3
  • Uvnc » Ultravnc » Version: 1.1.9.6
    cpe:2.3:a:uvnc:ultravnc:1.1.9.6
  • Uvnc » Ultravnc » Version: 1.2.0.5
    cpe:2.3:a:uvnc:ultravnc:1.2.0.5
  • Uvnc » Ultravnc » Version: 1.2.0.9
    cpe:2.3:a:uvnc:ultravnc:1.2.0.9
  • Uvnc » Ultravnc » Version: 1.2.1.0
    cpe:2.3:a:uvnc:ultravnc:1.2.1.0
  • Uvnc » Ultravnc » Version: 1.2.1.2
    cpe:2.3:a:uvnc:ultravnc:1.2.1.2
  • Uvnc » Ultravnc » Version: 1.2.1.6
    cpe:2.3:a:uvnc:ultravnc:1.2.1.6
  • Uvnc » Ultravnc » Version: 1.2.1.7
    cpe:2.3:a:uvnc:ultravnc:1.2.1.7
  • Uvnc » Ultravnc » Version: 1.2.2.2
    cpe:2.3:a:uvnc:ultravnc:1.2.2.2
  • Uvnc » Ultravnc » Version: 1.2.2.3
    cpe:2.3:a:uvnc:ultravnc:1.2.2.3
  • Uvnc » Ultravnc » Version: 1.2.2.4
    cpe:2.3:a:uvnc:ultravnc:1.2.2.4
  • Uvnc » Ultravnc » Version: 1.2.4.0
    cpe:2.3:a:uvnc:ultravnc:1.2.4.0
  • Uvnc » Ultravnc » Version: 1.3.2
    cpe:2.3:a:uvnc:ultravnc:1.3.2
  • Uvnc » Ultravnc » Version: 1.3.4
    cpe:2.3:a:uvnc:ultravnc:1.3.4
  • Uvnc » Ultravnc » Version: 1.3.4.1
    cpe:2.3:a:uvnc:ultravnc:1.3.4.1
  • Uvnc » Ultravnc » Version: 1.3.4.2
    cpe:2.3:a:uvnc:ultravnc:1.3.4.2
  • Uvnc » Ultravnc » Version: 1.3.6.0
    cpe:2.3:a:uvnc:ultravnc:1.3.6.0
  • Uvnc » Ultravnc » Version: 1.3.8.0
    cpe:2.3:a:uvnc:ultravnc:1.3.8.0
  • Uvnc » Ultravnc » Version: 1.3.8.1
    cpe:2.3:a:uvnc:ultravnc:1.3.8.1
  • Uvnc » Ultravnc » Version: 1.4.0.5
    cpe:2.3:a:uvnc:ultravnc:1.4.0.5
  • Uvnc » Ultravnc » Version: 1.4.0.6
    cpe:2.3:a:uvnc:ultravnc:1.4.0.6
  • Uvnc » Ultravnc » Version: 1.4.0.9
    cpe:2.3:a:uvnc:ultravnc:1.4.0.9
  • Uvnc » Ultravnc » Version: 1.4.2.0
    cpe:2.3:a:uvnc:ultravnc:1.4.2.0
  • Uvnc » Ultravnc » Version: 1.4.3.0
    cpe:2.3:a:uvnc:ultravnc:1.4.3.0
  • Uvnc » Ultravnc » Version: 1.4.3.1
    cpe:2.3:a:uvnc:ultravnc:1.4.3.1
  • Uvnc » Ultravnc » Version: 1.4.3.5
    cpe:2.3:a:uvnc:ultravnc:1.4.3.5
  • Uvnc » Ultravnc » Version: 1.4.3.6
    cpe:2.3:a:uvnc:ultravnc:1.4.3.6
  • Uvnc » Ultravnc » Version: 1.5.0.0
    cpe:2.3:a:uvnc:ultravnc:1.5.0.0
  • Uvnc » Ultravnc » Version: 1.6.0.0
    cpe:2.3:a:uvnc:ultravnc:1.6.0.0
  • Uvnc » Ultravnc » Version: 1.6.1.0
    cpe:2.3:a:uvnc:ultravnc:1.6.1.0
  • Uvnc » Ultravnc » Version: 1.6.4.0
    cpe:2.3:a:uvnc:ultravnc:1.6.4.0
  • Uvnc » Ultravnc » Version: 1.8.2.2
    cpe:2.3:a:uvnc:ultravnc:1.8.2.2


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