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.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| uvnc | UltraVNC | unaffected |
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Advisories
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Fixes
Solution
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Workaround
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References
| Link | Providers |
|---|---|
| https://github.com/ultravnc/UltraVNC |
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| https://uvnc.com/ |
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History
Wed, 01 Jul 2026 05:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | UltraVNC viewer off-by-one stack overflow in ServerInit desktop name parsing | |
| Weaknesses | CWE-193 CWE-787 |
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| References |
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| Metrics |
cvssV3_1
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Projects
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MITRE
Status: PUBLISHED
Assigner: securin
Published:
Updated: 2026-07-01T03:33:25.314Z
Reserved: 2026-05-05T04:03:22.622Z
Link: CVE-2026-7831
Vulnrichment
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NVD
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Redhat
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OpenCVE Enrichment
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